I am in the process of a G600 upgrade to my 2001 A36, and have the instruments for sale, here is the transponder. Please note the warranty that is included with the purchase price, and that it from a very reputable avionics shop here in So Cal. I will be listing the turn coordinator, and IVSI shortly. Below is the link to the eBay auction for anyone that may be interested.
Tim King KT 76C Transponder