which HTC device do you have?
Perhaps an old HTC Touch 3g is the right one? (315€)
It´s just 96g with build in Gps ... so no need for your GPS receiver.
Or perhaps the HTC Touch, but then with Bluetooth to your GPS receiver.
Just 112g and cheap .. 159,50€
I use the Qstarz Travel Recorder BT -Q1000 in an earlier version for two years. He is really small.
More than 30 hours battery power and a very good chipset sensitivity.
But you can get smaler recorder, too.
Look at this site.
www.qstarz.com