I changed the subject to be "GPS" instead of "GSP."
Some of the Garmin Geko 101 units sold are refurbished by Garmin. I purchased one for $60. Note that the firmware date inside it is 2001-2002. There are also some being sold as refurbished that are not at all, and they are simply used.
In the vast world of GPS multichannel receivers, that is quite old, and it can't be expected to lock up a position in anywhere near the time as a new design. However, if you have a minute to let it work, it is OK. I think it is slightly over 3 ounces.
Some purchasers would be upset to find that it has no map database capability, either for a topo map or for streets and roads. However, that helps keep battery consumption low. If I am out backpacking solo, sometimes I will mark my car's location for the return.