Pretty sure the people on this forum have been buying from this guy on ebay.
diyfanatiq on eBay
If you plan to get into coding those cables should work fine with an e53 if you plan on using the cable for other projects or new cars they recommend this one on this forum.
BMW Coding Forum
Car Diagnostic :: By Product Type :: INPA & Ediabas :: BMW INPA / Ediabas K+DCAN USB Interface - one-stop-electronics.com