What exactly are you locating? The company gibbons listed is a great place to look for a variety of tracers and testing equipment, but I have a little $200 in-ground tracer that has served me pretty well for years and is great for up to 3' deep.
The brand is Tempo and the model is a 508S. I bought mine at a CED, but I've also seen them at Walter's Electric out here in Cali.
Here's a link to an online retailer:http://www.valuetesters.com/Tempo-508S-Circuit-Tracer-Wire-Finder.php
It's cheap and I wouldn't bet on it for anything that I couldn't double check or verify, but it's great to have around and I'm not terrified at leaving it in my truck 24/7 because it may get stolen (my other tracers and test equipment that cost me more than $1,000 each stay at the shop until I need them). It's nice to have on a moments notice, and it's takes up very little space.