Are you talking a side drain or a bottom drain? I'd love to have a bottom drain on my keggles
You can always find parts to make it work (nipples, bushings, etc) and there are plenty 1.5" SS parts on EBAY for pretty cheap. If it is simply a 1.5" hole in the bottom of the keg then I guess you'll need a bulkhead fitting, which I bet are available at farm-supply stores for ag tanks. You can always reduce to 1/2" for using it with more standard homebrew parts.