I'm also searching for a bluetooth adapter. I've searched the forums and found the following that have a CSR chipset and allow firmware modifying:
Linksys USBBT100 Rev 1
D-Link DBT-120 Rev C1
Fujitsu Siemens BLUETOOTH V2.0
Aircable Host XR
Cellink BTA-6030 Bluetooth Adapter
The adapter must allow flashing of the external ROM, so finding the correct adapter is painstaking. If anyone knows of any others, please add them to the list. If you know where to buy any of the mentioned adapters (with correct revision #), post as well.