If you want to bond Lexan ( polycarbonate ) you can solvent weld it, achieving a clear "one-peice" joint with Methylene Chloride, but good luck finding it. It is generally considered a "professional only" product, but you may be able to get some from a sign maker shop that does outdoor signs. They use it alot, especially for hanging strips. Mention hanging strip glue if you go there, maybe they will sell you some,
It's not good for you, so its hard to find as joe Public. Some better R/C model shops carry good Lexan solvents, another option.
The other easier choice is IPS Weld-on #3 or some others they make : **broken link removed** It's thinner than water, and applied with a syringe or bottle with needle, capilliary action draws it into the joint. Don't do it on a really humid day though, it'll make the joint hazy or frostly looking.
You do have to make sure what material you use though... Lexan is GE Plastics tradename for polycarbonate, Arcylic is Polyacrylate, and uses a different solvent or "glue" IPS Weldon #4 is OK for acylics.
If you are really desparate to frustrate yourself, you can "weld" plastic with a hot air tool, and plastic filler rod. This is usually only done with things like ABS. It is something that you will try once and proclaim is for masochists. It involves a jet of low speed very hot air, a small filler rod, and is sort of like brazing. Damn hard to make look nice though.
Fibox makes very nice stuff, and the prices are about 1/3 as much more than the similar items you see at DigiKey made by Bud industries. Fibox has a bigger selection, and way more options though. I have used Bud cases, they are pretty good too. One more maker is Rolec Technocase, carried by Hammond in Canada, but alot of the sizes are hard to get. Hammond is now in the process of producing their own line of Rolec style cases, not sure how big the selection will be though.