I can't see exactly what you're dealing with, but if you do go with a
fiberglass panel, and you can't find a better way to deal with the need for a lip, you could add your own lip in
fiberglass (to the pre-made panel). It'd be a bit messy and fussy, but it's doable. Probably there's a better way though.
One note is that some of those "tile" panels are (I believe) some kind of plastic coating on a fiberboard backing. I wouldn't recommend those, but would instead lok for a solid
fiberglass panel. I'm prettty sure I've seen them there in "pebble" finish; I think you can get glossy too, although it might be somethin you'd have to order.
Or you might be able to get them online at someplace like McMaster-Carr. These would be able to be rolled up and shipped as tubes, I'm pretty sure.
Raya