Hey there, Shawn.
Theres a lot of materials you could use for figures. Putty is one. Epoxy clay can also be used as an alternative to putty. Lead foil or aluminum foil is great for straps, slings and even ponchos. Verlinden marketed the lead foil a while back but Im not sure if they still sell it. Aluminum foil can be had from milk tins, candy wrapper, etc.
Tamiya's Pla-paper is a very thin sheet of plastic that is very useful when making web gear. Unfortunately, its very hard to find nowadays and their catalogues dont list it anymore.
Hope this helps.