Before I bought my Garmin Edge 705, I was using an old Polar A5 HRM. The closest current model is probably the Polar FT4. The problem with my A5 is that it's nearly impossible to use without the manual. I can start and stop it and maybe figure out how to cycle between screens. Everything else needs so many key presses that I have to pull out the manual.
Still if you're willing to spend $100, I'd recommend searching eBay for a Garmin Edge 305. Prices seem to start around $90 w/o HR, $120 w/HR...