The front seating on a
Uhaul CT is very narrow and curved. No standard mattress or cushion will fit there so advice in that direction is irrelevant. OP is looking for a CT owner that is not using the original cushion. If none is available then it will be necessary to make a template, find a piece of foam that can be cut to fit and a cover made for it. Assuming that what she needs is the bottom cushion, and not the cushion for the top bunk which has a plywood backing with ends that fold, then using cardboard or heavy paper it would be fairly easy to make a pattern and cut a piece of foam using an electric knife. Covering it is another challenge and depends on skill level or paying someone to do that job. Part of our upper bunk was missing, and what remained for seating was quite uncomfortable so it was discarded and replaced with something else (casita chair)