It appears that Depron is gradually becoming scarce here in the U.S. I read somewhere that Depron is still being produced but not in the form that we use as modelers. That’s the bad news. The good news is that other foam board products are becoming available. And there are some products that we have come to love that are still available if you search around.
FliteTest has a new product available called Maker Foam. It comes in two thicknesses: 3/16″ and 8.5mm. Why mix fractional and metric measurements? Good question. When you look at the prices remember that you are getting folded sheets 30″ x 40″. Maker Foam is covered with white paper unlike the water resistant product that is brown. The white paper will certainly take paint better. Once I wrote FliteTest and asked if I could purchase a kit made with white foam board instead of the brown water resistant. The answer was a polite no.
Model Plane Foam offers a 6mm thick product made from extruded polystyrene foam. It’s not paper covered but they do mention it being sandable (sandpaper), so if you miss sanding with the other products and 6mm is the right thickness for your project, this may be a good choice for you. When you get to the product page you will have choices of: Grade A, Grade B, Mixed Box, and Seconds.