You might contact the conservation lab that works with, or refers out,
contemporary art objects, some of which are made with plexi:

Balboa Art Conservation Center
attn:  Janet Ruggles
P.O. Box 3755
Balboa Park
San Diego, CA 92163-1755
Phone: (619) 236-9702
Fax: (619) 236-0141


Anne Farrell
Museum of Contemporary Art, San Diego