Doug, if all else fails, there is a place in San Antonio, TX that I used to frequent called Plastic Supply of San Antonio. Their focus was more low volume custom work for signs, retail displays and the like. They had an actual showroom with very reasonable retail rates. I don't know if they will work for you, but worth a try.

102 West Josephine Street
San Antonio, TX 78212
(210) 222-8091