These are some Bluetooth dongle, which support changing firmware with dfutool and tuning with bccmd. There is no guarantee that they still support flashing and tuning when you buy them, because vendors often tend to change the hardware without further notice.
Acer Bluetooth Stick - BC2-EXT
Linksys USBBT100 Rev 1
D-Link DBT-120 Rev C1
DELOCK 61478
A7 eb502-HCI
Fujitsu Siemens BLUETOOTH V2.0 - BC4-EXT -there are no known revision for this dongle
Toshiba PA3455U-1BTM
Aircable Host XR
Cellink BTA-6030 Bluetooth Adapter
The adapter must allow flashing of the external ROM (BlueCore4-ext or BlueCore2-ext)
Acer Bluetooth Stick - BC2-EXT
Linksys USBBT100 Rev 1
D-Link DBT-120 Rev C1
DELOCK 61478
A7 eb502-HCI
Fujitsu Siemens BLUETOOTH V2.0 - BC4-EXT -there are no known revision for this dongle
Toshiba PA3455U-1BTM
Aircable Host XR
Cellink BTA-6030 Bluetooth Adapter
The adapter must allow flashing of the external ROM (BlueCore4-ext or BlueCore2-ext)