Are you looking to buy local or online?
If you can wait, and buy online, I'd suggest a GENUINE HTC charger identical to the one that came with your phone. I have 3 of them total and they work exceptionally.
Just be sure it comes with a genuine USB cable as well. Some people don't use the right cable, and they get half the current as a result. You should be able to draw 1 amp (~900mA) of current when your battery is less than half full. This is how you can test the performance.
Download current widget and while charging, look at the current being drawn. Actually, the screen uses up current, so turn off the screen and let it charge for a few minutes. Then turn on the screen and check the current draw really fast.
Keep in mind that the charge current gets lower and lower as the battery fills up. Don't be surprised if you're only charging at 125mA at 90% full. That's normaly. I suggest charging from like 40% or lower for this test.
You should also see AC charging in the Battery Status under the Power option in settings. If not, it's the wrong USB cable most likely.
If you have to buy local, maybe Best Buy's brand Rocketfish would do OK. It will probably be $20+. If you buy from reputable sellers, and the charger is cheese funk, you can return it with little hassle.