The only 'special' one I know of is for the Hei Hei frames.
They used a variant Kona called the 'CAT' collar which referred to something like Coefficient of Alternative Tubings and was intended to prevent binding of disimilar materials (ti. and steel).
Apparently this could occur from friction heat generated in the frame via over-exertion of the seatpost / seattube during long hours in the saddle.
Depends if you want to be completely 'period correct' however, as this type was only (I think) used during the '92 - 93 crossover period.
You might have difficulty finding one independant of the frame though (as they are pretty scarce), but they're easily identified by a Bagpuss-esque motif engraved on non-driveside face.
Hope this helps,
BB