Tap Plastics (tapplastics dot com) have lots of different sizes and shapes of acrylic rods and flat pieces. If you live on the west coast you can visit in person and dig through the 'scrap bin' for flat pieces of clear plastic and also pieces of hollow and solid tubing in several shapes. They also will cut full size pieces to any length you desire. Additionally they have wonderful plastic boxes, jewelry molds - usually cheaper than I've seen any where else, resin, clamps, glues etc. The best part for me is that they are not a craft store so their pieces are hugely cheaper than craft stores or web sites.
My local store has cut and sent me items through the mail when I couldn't get to the store and again for very reasonable prices. If they aren't busy, they've also helped me check my design for an acrylic shadow box and then cut the pieces for it with their hyper accurate saws. I took the pieces home, glued them with some rather smelly adhesive. A day later I had a display that I used for years at doll shows to display small items do they could be seen from all angles without risking breakage, dirt accumulation or having the piece grow feet and walk away.
Best of luck!