Why bother? You can get a 50mm stem for $50 or less. Adjustable stems are $20, but are weak and flexy most of the time, and just one more thing that could go wrong.
If you are using a BMX handlebar you can get one for $20 or so, check at BMX shops. If you are using a 1" threaded headset, they are even more cheap.
Here's a nice Synchros mtb stem for $35 shipped. http://compare.ebay.com/like/1108362...Types&var=sbar