AR Auto Service provides a ton of trackside support to the HPDE community. I haven’t had the chance to deal with them directly, but they have a good reputation. The tech they send out to Audi Club events -Dan, is a super nice guy. They’re in Lake Oswego.
http://www.arautoservice.com/
Small shops in general can either answer phone calls or work on cars. I don’t know anything about Autohaus Bayern, but if it’s just 1-3 techs, it might be worth popping in to inquire rather than wait for a call or email back.