I'm not sure of any you can send payment in, if you are looking into that payment method, try ebay. When you are finished with the moniter you can make your money back by re-selling it.
Also try amazon. I bought mine off ebay, it's exactly like the doctors, we only pay with money orders. It's not really taht much more then it would be for you to rent itfor a few months, and then you get to make the money (or some of it) back.
Best of luck!
I too have a Bebe sounds one from walmart, it doesn't work until well into the 7 month - says so right on the directions. I couldn't wait, had to get the other one.