I spent quite a while looking for one myself, and I came away finding only PS2-to-DC converters.
I guess you could get one of those, and reverse the wiring. Or you could have someone here or at Shoryuken's forums that builds arcade sticks possibly make you a breakout box. Either way, it's not going to be easy or inexpensive.
Personally, I lucked out and grabbed a Tekken 5 stick at Gamestop new for $25 in March (last one in the entire company, I was told). I would have loved to use my DC Agetec stick, but it was not happening.
You may be able to snipe a Hori T5 stick off ebay...being that it's summer.