You requested it, and we listened.  This D shaped toilet seat is suitable for 353mm width pans and is available in both a regular (114-206mm) and wide hinge (200-230mm.)  The D Wide features all the standard qualities of the RTS range; soft-closing, made from Duroplast, easy release system for cleaning and adjustable hinges.  This quick fit seat can be installed in minutes and comes complete with both top and bottom fittings.

https://www.replacementtoiletseats.co.uk/ourshop/cat_1414814-D-Shape-Toilet-Seats.html