Not sure where you're located, but you could try the Galloping Ghost (arcade) outside of Chicago. I know they had an Aliens, and I think it was in an original cabinet with art too; they go out of their way to have all of their stuff as-original, everything from the hardware setups to the cabinets and art too. Anyways, super-friendly guys, and worst-case they might be willing to send you hi-res pics of their cabinet art if they don't have a source for ya.
Probably easiest to call, but here's there site too: