If you're making your own pots, what about using marbles as feet? They come in plenty of colors and sizes. Will withstand temperature changes and water. You could create a socket on the bottom of each pot that would take a marble to be glued into it.
Or... using bolts with nuts on the ends, to give it a more industrial look. Again... use the bolts as the male part for the created socket on the bottom of the pot. Then use the nut as a foot print. If they rust, it will give it an interesting look. They're also nuts and bolts that are weather resistant.