If the back of your patch has the sticky side of velcro on it you can make a band the is just big enough around to wrap around your girth. Sew some fleece or something on the horse side of the band so the patch will stick to it. I think when I got my heart monitor a strap like this came with it. Is kind of hard to describe, but I hope you can envision it.
I am having trouble keeping the one end of the heart monitor keep contact with my horse. The part that goes under the saddle stays fine ? the Velcro sticks to the pad, but the end that goes under the girth keeps slipping out since there is nothing that the Velcro can stick to. Anyone have any suggestions?