I ran a plastics warehouse over thirty years ago. Plexiglass was high then.
Thomas registers lists manufacturers. Cadillac Plastics nearly always had what I needed, but higher.


http://www.delviesplastics.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=DPI&Ca...

They'll cut and polish edges...
Check with the local plastic pipe outfits. Irrigation supplies,
Lowe's, high, and I can't stand home depot, Haven't even walked in in over a year.
Might hafta call a sprinkler installation outfit and see where they buy timers, valves, heads, etc.