I love he Jawa in R2 costume; great idea!
As for your question about glues: I use a plastics-only super glue that I bought at a local Home Depot. It comes with a small bottle use to prepare the surfaces of the two pieces of plastic you want to join and then a second bottle of the actual glue. (Cant remember the name brand off the top of my head, but its the standard brand sold there.) The glue must be held together for about 30 seconds to achieve the "hold" you want. It works pretty well for holding weapons, as well as figure parts, together (at least in my experience).