I use PVC, but than a special sort. The lite one version which is like a very strong foam with very litlle gas bubbels. You can buy it in different colours, but white is the most common to get. Ask for Forex, its a trade name, than the people probably know what you want. I bought it at a store for all kinds of plastics. Costs about 40 Euro/m2 in just 1 cm thick.
It's easy to work with and epoxy sticks to it very good, also easy to bend.