There is a precedent for MWK tools for profession skills in the description of the Traveler's Any-Tool.
This implement at first seems to be nothing but a 12-inch iron bar lined with small plates and spikes. It can be folded, twisted, hinged, and bent, to form almost any known tool. Hammers, shovels, even a block and tackle (without rope) are possible. It can duplicate any tool the wielder can clearly visualize that contains only limited moving parts, such as a pair of scissors, but not a handloom. It cannot be used to replace missing or broken parts of machines or vehicles unless a mundane tool would have done the job just as well.
The any-tool counts as a set of masterwork artisan’s tools for most Craft or Profession skills (although very specialist crafts such as alchemy still require their own unique toolset). It is an ineffective weapon, always counting as an improvised weapon and never granting any masterwork bonus on attack rolls.
But if you actually want to buy a MWK tool for Profession: Sailor, then you should look at the paragraphs of the MWK tool.
Several common items already count as masterwork tools for particular skills. These are the alchemist’s lab, climber’s kit, disguise kit, healer’s kit, masterwork musical instrument, and masterwork thieves’ tools. Therefore, there is no masterwork climber’s kit, masterwork healer’s kit, and so on—those items are already the best available for general checks with the relevant skill.
Some skills have no appropriate tool or masterwork tool—no non-magical item exists that grants a bonus for all uses of that skill. For example, just because a certain perfume is favored by local nobles (granting a +2 circumstance bonus on Diplomacy checks to influence them) doesn’t mean that perfume has the same effect on a member of the thieves’ guild, a foreign berserker, or a medusa. Likewise, just because a fake beard woven by dwarves out of the beards of famous dwarves may grant a +2 circumstance bonus on Use Magic Device checks to emulate the dwarven race doesn’t mean the beard has any effect on using that skill to activate elven items or paladin items, or to decipher a written spell.
Individual GMs may want to allow masterwork tools for other skills at the listed cost. The circumstance bonus for such a tool should never be more than +2. The tool should either have a limited number of uses (such as the disguise and healer’s kits) or only apply to certain aspects of the skill (such as the balancing pole’s bonus on Acrobatics checks to traverse a narrow surface or the magnifying glass’s bonus on Appraise checks for detailed items).
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As you can see, you can design your own MWK tools for any skill with your GM's approval. But these should have some kind of limitation. Like how the Healer's Kit is used up after a number of uses, or how a Balancing Pole only grants a bonus to Acrobatics checks to cross narrow surfaces.
Profession does however seem to function like Craft, in how it grants a +2 to all instances of the skill without having a set number of uses. So a lenient GM would allow you to get a MWK tool for Profession: Sailor which grants a +2 bonus to all checks.
Is this for PFS play or homebrew?
This tool is perfect for its intended job. It grants a +2 circumstance bonus on a related skill check (if any). The bonuses provided by multiple masterwork items do not stack. [...]
Some skills have no appropriate tool or masterwork tool—no nonmagical item exists that grants a bonus for all uses of that skill. For example, just because a certain perfume is favored by local nobles (granting a +2 circumstance bonus on Diplomacy checks to influence them) doesn't mean that perfume has the same effect on a member of the thieves' guild, a foreign berserker, or a medusa. Likewise, just because a fake beard woven by dwarves out of the beards of famous dwarves may grant a +2 circumstance bonus on Use Magic Device checks to emulate the dwarven race doesn't mean the beard has any effect on using that skill to activate elven items or paladin items, or to decipher a written spell. [...]
The tool should either have a limited number of uses (such as the disguise and healer's kits) or only apply to certain aspects of the skill (such as the balancing pole's bonus on Acrobatics checks to traverse a narrow surface or the magnifying glass's bonus on Appraise checks for detailed items).
Nothing in the rules restricts masterwork tools to Craft only, and a number of examples show its use for non-Craft skills. There's no reason, then, to believe that Profession skills are off the list.
That said, you need to have a link between the proposed tool, the proposed skill, and the proposed use of the skill.
For example, a masterwork sextant should give a bonus to using Profession (sailor) to navigate, as would an annotated copy of a book like Norie's Seamanship. However, neither of those will show you how to tie a sheepshank knot.