Go to the fabric store and buy a piece of black craft felt. Get some spray adhesive. I used 3M 77. Spray the existing liner (after carefully beating the dust off it and making sure it'* dry) and the back of the felt. Follow the waiting time on the can. Then put the two together, and trim with a razor blade, and poke something through the holes. Work it press it, work it, press it as it dries to make it follow the contours. Then stencil and spray paint. I used Avery label paper, in full sheets. Print your pattern, cut it out, and stick it on for stencils. Press hard to make it stick so the paint doesn't wick under it.
The retainers are re-usable a couple times. Just be careful pulling them off. If any break, the dealer can get them for cheap, or I can give you the part number.