Simpson Ltd. has them from time to time...
For example:
http://www.simpsonltd.com/product_in...oducts_id=2422
I have been told by Simpson Ltd. that a C&R FFL is sufficient for any of these Interarms Mauser Parabellums... however, it might be wise to verify with BATFE 1st!
Good luck with your quest!
NICE pistols