I was in your same position. I didn't have the $500+ budget to get a decent wireless system, but needed good quality lav mic.
I ended up getting this wired lav mic. It's got a 10 ft. length, which is long enough to stretch out to get a medium shot interview style (like top half of abdomen up) at 35mm on my GH2.. which equals just under 50mm on a 7D.
http://www.bhphotovideo.com/c/product/266176-REG/Audio_Technica_AT899_AT899_Condenser_Lavalier.html
For longer focal lengths, I just plug the mic into a long XLR cable extender (I think mine is like 25 feet) and as long as it's a sit down interview (not walking around)-- it works out as the same functionality as a wireless system for a few hundred dollars less.
I use a Zoom H4n, which is able to provide phantom power to the mic. I highly recommend it. The Tascam DR100 gets raving reviews, too. I might have considered it instead of the H4n, but I was already accustomed to it from working with other folks.
I also HIGHLY recommend getting one of Sescom's cables. This lets you plug the cable into the headphone jack of your audio recorder. Then that cable has a Y split (two cables off of it). One goes into your camera, so that the audio gets recorded onto the video without having to sync it in post. The other has a headphone jack to plug in your headphones. NOTE: The Tascam I spoke of has both a line out jack AND a headphone jack, but most of the others just have the one output for headphones. The cables also come with a 25dB Attenuator Pad if that model camera needs it. The GH2 does, and I think Canon's offerings do as well.
Let me know if I can help otherwise. Myself, I'm looking for a decent, cheap boom system for around $300 ($200 would be nice, but I don't think that's going to happen). Any suggestions anyone?