I have gotten some very promising results with a $50 sports GPS, the Canmore GP-102+. Sirf4-based, 1 Hz, .fit format files. Misses features that would be required for records, but seems more accurate than the GT-31 (no big surprise with the newer chip). I posted some initial results at boardsurfr.blogspot.com/2014/07/a-smaller-better-cheaper-gps.html

This is just a quick blurb, in case anyone else wants to test it. We cannot get any GT-31s in the US anymore, and this GPS seems a better choice than older "approved" Garmins. I have 2 more units on order for more testing.