We used to have a '68 GMC dump with the 5speed/2 speed setup and I might recall that the axle cable was strapped to the stick and shared the same hole in a round bellowed boot.

What jumps to mind is one of the "small 4x4" with the transmission stick and T'case stick sharing the same two hole boot.

Anyway, look on eBay for truck transmission boots and I bet you'll find one that'll work.