Bought on ebay for $45.98 ($33.99 + $11.99 shipping & handling). Also sold by Adorama $105.95 ($99.95 + $6.00 shipping & handling) and B&H $104.40 ($99.95 + $4.45 shipping & handling).
It did not come with instructions and so I had to fiddle around with it for a while. Could not get it to work until I discovered that the battery in the receiver was covered with a clear plastic shrink wrap. It then took a few more minutes to figure out that I had to turn on the receiver my pushing the orange button for a second. Works great so far! The receiver takes a CR-2 3 volt Lithium battery and the transmitter takes a A27 12 volt alkaline battery.