As for making it yourself, I think that the Jell-O they sell at wall mart does the trick just fine.
Hardware store 'Epoxy Clay', 'Kneadable Plastic', 'Plastic Clay', 'Metal Clay' is what you are looking for. Milliput or Apoxy scult is a little nicer to work with but they are not as readily available and it is a simple mod anyway.
What about posting in the right forum next time by the way?
I use apoxie sculpt. If that's not really an option for you, I think there's something called aqua mend. I heard that it's really cheap and you can get it from Home Depot.