The one to go for guys is a Holux GPSlim 236.

I bought one of these from ebay and its MINT!

charges using mini-usb, locks on to satellites within SECONDS, and is bluetooth.

i think there is a shop on ebay that sells them for 82 delivered.

As jim says, DONT BUY A CHEAP ONE. Ive heard some people having to wait 20 mins for a lock-on PMSL