who makes the best shift cable bellows?
Is there any aftermarket ones made out of a better material?
I got a remanufactured HP transom assembly from vinzi marine in florida and my shift boot is leaking already in only about 30 hrs. Im pretty sure he used the cheapest one possible as he built a very poor transom assembly.

im guessing i should buy the merc one?

I am no expert but you generally get good quality with merc. If I didn't see anything that looked better then my default would be Merc.!

Anyone know where to buy the tool to clamp the little steel clamp on the bellow?

You can substitute the steel clamp with one or two tie wraps instead.
Don't pull them to hard though, it is good if the bellow can slide on the cable with some friction.

I usually throw that steel clamp away, use a tie instead. As far as quality, Merc bellows are the best fit and last longer than any aftermarket bellows.

I bought the sfift cable kit from CP not sure what kind it was but i wanted it fast thats why i went threw them