Call a local hobbyshop, I used to live in upstate, and even out in the 'daks I could find a "local" hobby shop. But call them up and see if they know of anybody who does custom canopies.

Vacuum forming and casting still has a lot of applications. 3d printing is not the end all manufacturing technique, there are still a lot of things it doesn't do as well as others.

In this case, a crystal clear plastic canopy would probably be best done with injection (Which usually takes lots of 10,000 or more before a lot of companies will considering running it, some less) or vacuum forming, which you can setup in your garage. If you can find a local 3d printer who can cheaply print that out as is, regardless of the material, there's your mold for your vacuum form. Just sand down the mold till it's smaller by the material thickness you'll form.

Also, having the experience of a small VF rig, you can easily enlarge it to do custom fuselages and wing shapes. Again, while 3d printing will work for that, a VF plastic shell would seriously reduce the weight without losing much strength.