boatboy, take a look online at what the plastics manufacturers have to say. PPG, Dow, GE, Rohm & Haas, whoever is in the game today.
Most of them have installation guides online which will show you the methods you can use. VHB tape is a great option, it holds windows in skyscrapers.
But on the glazing material itself, you don't just want to go to the local plastics place and buy "plastic". Every maker, every plastic (acrylic or polycarbonate) comes in different grades and unless you buy UV-resistant and scratch-resistant material, designed for use as exterior glazing, you will be disappointed in how the usual cheap stuff (intended for napkin holders and towel racks) holds up on your boat.
Buying the right stuff is going to cost more up front, but last way better on the boat.
VHB tape, like everything else, can be ordered discounted from Amazon, but some of the vendors will take a month to ship it, as they batch order it from 3M. Worth ordering ahead of time if that's what you need. And 3M also has web pages explaining the different colors, thicknesses, and widths of tape available.