The design is somewhat unique in that the shift lever spends most of it's life (in 2-Hi) parallel to the floor, horizontal. When it's in 4-Low it's vertical next to the seat. The boot accomodates the full 90 degree range of motion. The bellows convolutions are offset so it appears to be at ~45 degrees in it's natural position. The designs I've seen available are typically for vertical shift levers.

For about the past 25 years Big Tan has had the transfer case shifter sealed by a thick piece of rubber with a slit ~12" long. It works well enough to seal the air from below from coming into the cab. If worst comes to worst, I'll continue with this. But if others are interested in the same thing, it may be worth considering a custom fabricated part.