Quote Originally Posted by Marc Zeitlin View Post
I don't know what your plane is worth, but this:

http://www.uavionix.com/products/echo-uat/

is only $1K, and works with your existing transponder.
From their web site: "UAT ADS-B Transceiver for Light Sport and Experimental Aircraft."
My airplane, a Cessna C-150H, is unfortunately a certified airplane, so the above is not "legal" or "certified," according to the ever-helpful FAA.