Go ahead and buy a new one, it's well worth the dollars, and will give you a warranty. Think of it as an investment in your training. I personally feel that training by heart rate is the best way to judge your efforts across all 3 sports.
also i would recommend you look at this one: this is what i got, and for $82 you get the HRM and footpod so you can actually see your pace and distance on the watch as well which is neat. that is my opinion of course.
Just got the one on amazon for $88, cost me about 35 US dollars to ship here but still like way cheaper than what I can buy in stores or even 2nd hand here in NZ.