Have a surplus strap for Garmin ANT+ heart rate devices. Brand new never used (I already have 2, so really don't need a third). It is of the old design, i.e. rubber centre section and NOT waterproof.
Compatible with forerunner 50/60/305/405/310XT and edge 705. It is an ANT+ one so probably compatible with all new Garmin devices that use ANT+ and other brands too (see here http://www.thisisant.com/modules/mod_pr ... ct&prod=54)
Currently sell for around £26 to £40. All reasonable offers accepted.