I have a polar ft40 (
http://www.amazon.com/Polar-Womens-H...dp/B0035XOYH4/ though mine was apple green) which I love. I've had it for two and a half years now and use it a lot, works great. I did have to replace the strap after 2 years when I started to have problems, but no problems now!
Overall Polar is a really good brand for hrm, and they have some cheaper simple models too like the ft7. You might also have luck trying craigslist, though not sure about this time of year when everyone's buying stuff like this for their new years resolutions
.
I would say getting one with a chest strap is better, as it will generally give more accurate readings.