suggestions for new owner

Congratulations for your Porsche 928 purchase. There are some interior bits that may be available new.  There may be some good used bits available in good condition.  There are upholstery shops that work on the seats.  But short of finding a specialty shop or using Porsche Classic restoration there are no “one stop” shops that I’m aware of. Depending upon the condition of your interior, it may be less expensive to locate a parts car with the major interior bits needed. 

928 International ( 928intl.com ) is a major dismantler that may have the parts that you need.