I would generally start by trying to find an already existing item that emulates something close to the feat you are trying to create an item for {ie an item in the same category of feats, the same level, and if possible, the same class.} This way, you could use it as a template of sorts when you create the new item, with caution, as there could be a reason why such an item was not created.
If I were to make something like Rod of Reach, I would generally follow the pattern of the 'Wands of Widening'. {Specialty Wands found Here } Basically, if I had to do a quick conversion, I would just change the 'Widen Spell' effects for the 'Reach Spell' effects, rename it a 'Wand of Reaching' and follow everything else {price, item level, level of spell that could be empowered by it, a small change to its crafting to reflect a spell that could be empowered by the Reach Spell feat, ect.}
As for something like a Rod of Quicken type effect, it may be just to powerful for this edition. In my {quick and lax look} of the items, I have not found something which emulates a 10th level feat, especially one that can only be used once a day by those that have the actual feat. If I had was forced to make to convert a Rod of Quickening type effect, I would most likely have it follow the same template as the 'Wand of Widening' but have the whole line item level start at 13 {so a 'Wand of Quickening <1st Level Spells>' would be a 13th level item that would cost around 3,000gp, using other specialty wands for the price. This is because wands item level is 3 levels above when you would be able to gain the feat, like when the Wand of Widening item level line starts} Every two item levels, like other Wands of this type, there would be an upgraded version. As for levels not covered within the LV20 item level, you could say they exist, but there akin to an Artifact, something which not mortal can create.
Anyways, to make a long story short= 1) use other items with similar feats as a template 2) the furthur away from the temeplate you go, the more careful and the more you should question if you should convert the item, as PF1 is a much different game then PF2 and 3) once you do a conversion, look at it really carefully, because there may have been a reason why said type of item as not made its way into PF2 {it may be because it breaks the game, or it could be because of time restrains and it will get added.}
