there are lots of otc licenses avail. depends on where you are going. don't have a phone book handy but but i think a place in anchorage called wild rivers alaska.
http://www.alaskansportsman.com/dire...ting/index.php
http://www.alaskaraftandkayak.com/
these links could be helpful.
for just caribou think about haul road trip with raft / canoe. if you are a very good rafter you might look into atigan river to sag . antigan canyon / gorge can be very dangerous. have friends that have done it but would like it thru one area if they did it again.
Gulkana could be good for moose and maybe black bear but probably more brown bear and you would need a guide unless you have a close relative as a resident here in Alaska there is a portage on that river and i beleive it is a 3 days float.
thou some day i would like to do the atigun trip but i'm just a novice.
better trips are probably fly in but friend lost all his meat on a moose hunt because they could not get the meat out quick enough.
some of the air charter services that are big game transporters may supply rafts and gear. Rust's air might ????try a search for big game transporters.
good luck- pat