[One of Many]

Torispherical domes from metal might be readily available for about $100usd.

One done from plastic is going to take some time to create the tooling and find someplace to get it formed, trimmed to size, and ready for testing. If you do not have much time to find access and complete either portion of the tooling or plastic forming process, you have nothing to work with. As an alternative option, you might even find a vessel tank end cap to use as a die to form your plastic one on.

Do your theoretical answers require a specific material strength? Can that theory be scaled to suit what you end up with, or is the dome shape of your own design that you expect to test prove your pre-calculated theory based on a torisphere?

Would laying up fiberglass cloth and resin work?

In the US, $100 might get you between 1- 2 hours of a professionals shop time. I'd say those with experience that could make this as a custom plastic cap for you may have 1-2 days of labor to do the die and at least 1/2 day setting up and forming it. A minimum of 12hrs shop time blows your budget here in the States. Your only choice is to find out what that 12hrs might cost you if you do find a plastics shop in your home town.

Doing it on your own? You will need to locate a plastic sheet supplier and find out how many 1cm x 50cm sqaure blanks of plastic $100 will buy. How many of those can you afford to waste trying to get a usable one? PVC forms nicely and is one of the cheaper ones.

I see this taking some networking on your part to find the plastic sheet supplier, who may know a place that thermal forms and those that thermal form know who makes thermal forming tools.

DC