Why don't you just use a real sandwich?

Carefully painted, almost anything can substitute for real food. The trick is finding objects with the right texture to capture the paint.

Cut bread-shaped slices out of white foam rubber of appropriate thickness. Color the edges with a brown magic marker for white bread. Lightly "mist" the bread with brown spray paint for toast, or whole wheat.

Use scraps of leather for the "corned beef." These can be hot-glued or even hand-stitched to the foam rubber to prevent the sandwich from falling apart.

Poker chips (again, carefully painted) can be pickle slices. You can use a scrap of green fabric for lettuce.

Don't forget to paint part of the inside with bright, yellow paint for mustard.

Good luck.