Extra parts? Well for now my guess and simplest would be to buy another and have a near complete parts source. Not very many built, no support for parts even tho the military has to have something in a warehouse somewhere.
For now the 1161 will be sold until supply is exhausted. Then I would bet that all the sudden the parts will be found, horded to drive up cost. If I had to support one I would buy a complete, semi complete unit as that will be more cost effective than buying a single replacement part.
As for the shop manual, TM, If the manufacturer has none to which that is hard to believe as the Military may require one, what do you tell your equipment buyer? Your out, unlikely but the better reason would be a liability issue now that the 1161 is being surplussed out.
Good luck, and buy another unit.