I have 1 Polar Heart monitor strap, new never used, size medium. Still has the little belt that holds it together; just like you’d receive from a retailer. I know for a fact that they work on T31 and T61 chest straps. Beyond that, I’m not sure. $6.50 shipped via 1st Class Mail. Paypal preferred. This is only the elastic strap. Does NOT include the chest transmitter.
This is the ELASTIC STRAP:


It works on transmitters like this, but NO transmitter is included. ONLY STRAPS are for sale:


