@bruce: A number of vendors will allocate you a PID from their VID if you’re using their IC’s (Atmel and Microchip do from memory, but I seem to remember something about ST not being so generous unfortunately) - it’s the only sub-allocation allowed by the USB-IF.
*edit: It looks like ST does too, just you have to contact them about it: https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=%2Fpublic%2FSTe2ecommunities%2Fmcu%2FLists%2Fcortex_mx_stm32%2Fquestion%20for%20STOne%20or%20anyone%20from%20ST%20(about%20USB%20and%20allocating%20PIDs)¤tviews=2502
*edit 2: And TI does also.