If szakcajaru is around I tried to reply to your PM but it won't go through. My reply is here:
Hi again RPE,
If you need a links to the basic PTX transponders they are:
http://www.team-mrt.com/mrtwebshop/x16174.htm
http://www.team-mrt.com/mrtwebshop/x16183.htm
The price shows in UK GBP (not US$). If you click on 'Buy' you will go to our online store checkout page, you need to select the country for delivery as USA (using the dropdown selector) the prices will then be shown correct without UK VAT (tax). The price for 1 transponder will not show any shipping charge, it's free shipping. Shipping is charged for 2 or more.
Hopefully you should have the information you need.
Regards,
Terry S