I got mine from RepairsUniverse.com. It was 67$ with shipping. Order their double sided tape, too. When you get it, disassemble according to their YouTube video. To remove the glass, use a hair dryer to heat the glass, and nudge it out with the plastic tool they provide. If you go slow and don't rush it, the whole process will take about an hour the first time. Clean the frame well, and place the tape on it. You'll have to cut the piece provided, so don't worry if it doesn't line up exactly. Press the glass down on the tape and reassemble the phone. BOOM.
Also: if you want to do something REALLY cool, search for the white digitizer and battery cover. The all white G2X looks awesome, and you can get the whole kit for like 80 bucks USD.