This is where the $2.00 power transformers from Goodwill come in. You can find practically any voltage power brick for cheap. Just find one that outputs approximately the voltage you need, cut the end off, and wire it up, plug it in to your power strip, and off you go. Its much safer than pulling power from your CPU power supply.
Second hand stores are a gold mine for saving money on electronics. Its good for speakers, motors (buried in blenders, cassette players, and the like), cables, plugs, keyboards, switches, knobs, etc. Its also a great poor man's hardware store. Need that special spring, hinge, clear tube, thin plastic thingy, check the kids toys section. How about a strip of leather, small mirrors, sheet copper, check accessories (belts & purses). I also frequent the dollar stores for similar items.
Regarding your buttons, you might try tracking down an arcade distributor/repairman somewhere in your town. Through a little research, I found two in my small 35K population town. They are both elderly guys, one out of a warehouse, and the other out of his house. They both have boxes & boxes of various arcade parts. You've probably got someone like that within 10 miles your house.
With your artwork, you could make an old coffee table look hot. I can't wait to see your next project.