i have a couple of orchids mounted on clay pots... i got cheap pots from the 99 cent store, plugged up the bottom hole with some polymer oven bake clay... then drilled two holes on them with a diamond hole bit...
here's a cattleya i just mounted the other day... shows the plug too...
you can get some at walmart in the art section that don't have the hole in the bottom... also, micheals i think... but if not, you can get some polimer clay for 3 bucks and plug up a bunch of pots in a toaster...