Any recommendations?

Yes, buy a hang gliding/paragliding vario and use the paragliding leg strap to mount it to your thigh. Flytec makes a variety of models and you can find these used on the OzReport.com if your are looking for a break. These often have many features such as logging of RoC, altitude, 2 altimeters, clock, etc.
You will have to be careful about ignoring climbs from large speed changes but I have found these to work well especially in less slippery older sailplanes.