I traced my toilet seat on a sheet of butcher block paper, cut it out and took it to Lowes. I now had a template of the original. I walked the aisles at Lowes, found the toilet seats and found one that matched almost perfect. Mine was not oblong, but you can do the same with yours. That way, you know if it will fit or not.
As far as the holes for attaching? They are all identical. Same width for RV toilets and residential toilets.... and actually ... commercial toilets too.
Make a pattern, take it to a Home Improvement store, and just match it.
(Showing-off my Bidet install).
Wooden seat, replaced that cheap plastic one that came factory.