ABM 260DP and AMB 260x transponders for sale. $400 each shipped to the lower 48 states. These do not require subscription. The 260DP comes with a fused cable you could wire to the battery with a little crimping or soldering. The 260x comes with charging cradle, 110 plug in cord and car charging cord, plus one mounting clamp. 4 blinks when fully charged. I sent this one out to get the battery replaced a few months ago, so it is scarred up, and epoxied back together well.
i'm interested in the removable one with the clip but PM your lowest price. my race org can provide them free but I hate having to remember to take it back at the end of the day