When I had my SP89 configured into a MP5K RTDS did the work. Now I would most likely send H&K work to Ken @ TPM Outfitters, simply because it closer. https://www.tpmoutfitters.com
make sure it's done correctly or else you're doing a fun but illegal conversion that requires an 07 with SOT. TPM did some work for an old shop I worked at. Good work, bad service.