So in my campaigns I normally give each player an extra nice magic item at some point in the game. Its normally custom made to fit the character and I have a gunslinger musket master. This is what I came up with... (too powerful?)
The Eye of Heaven
(A scope)
The Eye of Heaven is a telescope made to be mounted onto the top of a gunslingers weapon. The Eye of Heaven gives a +2 bonus to attack. If the gunslinger uses a full round action to steady the weapon the Eye of Heaven allows a +5 attack. 3x/day true strike may be used and 1x/day true sight.
I'd say that is a bit powerful, especially when the gunslinger gets access to abilities such as Dead Shot and Death's Shot.
I'd give it a +1 equipment/circumstance bonus that improves to +3 whenever you take a full round to line up the shot. I might even say that it is part of using the weapon, so it would stack with attacks which are already full round actions (or less if the character is willing to extend the action) such as VitalStrike and Dead Shot.
There was even a thread a while back that places the cost of a charge of True Strike at around 1,800gp, and while the precedent for true seeing exists (crystal of true seeing) is there, I'd say it should be considered carefully and only apply when looking through the sight.
Instead of these spells I'd suggest simply combining the Far Reaching and See Invisibility Sights from Ultimate Combat. Being able to extend the reach of your ranged touch attack without spending Grit is pretty big for a Gunslinger, and being able to find invisible creatures and ignore the effects of invisibility can be useful for any character (if slightly situational).
But if you really like the thought of giving an occasional True Strike, feel free, just make it cost a standard action to activate, as per using the spell normally, unless this is planned as a high-lvl item (in which case, I suggest looking up the "balanced ring of true strike" and similar threads).
Thanks for the imput! Exactly why I posted =) I'm not as up to speed with the gunslingers higher level abilities. Thanks again.