He pointed me to
www.muellercorp.com and Glenn Mueller emailed me back and recommended I contact Mike Mancini at Instrument Specialties, Inc. I guess Mike batches parts for Glenn so I'm waiting to hear back from Mike. I know Instrument Specialties from other discussions here and, if I'm not mistaken, they have a good rep.
Sad to here Advance no longer does plastic, however Mike Mancini at Instrument Specialties is a top shelf service, I've been to his shop, seen first hand that Mike and his people turn out nothing but quality work
