Worth a look are the following from Lifesaving Systems Corp based in Florida (
www.lifesavingsystems.com):
#406 Medevac Litter - Although a basket, it breaks in half for stowage, weighs about 40lb and is pretty stable when empty on the end of the wire. They also do a titanium version which is half the weight.
#402 Medevac Litter - A basketless litter.
#450 Medevac Board - Two piece spinal board.
All the above are in widespread use with the USCG and USN.
Hope this helps.