By any chance? is there a makers name on the underside of the Cistern lid??
If so that could be a start point for Google?
There may be names and code numbers on the inner surfaces of the cistern?
Having said that, if the WC is more than say 5 years old then there is a very high probability it is no longer available?
OK now what you may? have to do is to carefully measure the distance between the studs emanating from the WC and pick up a "replacement" seat / lid that has dimensions to fit. The pattern of hinge may alter from that indicated in your image.
One trick to watch out for is to determine what type of fitting, is fitted to the "stud" protruding from the WC pan. there are 2 common fittings, one is a through screwed thread screw with a wing nut holding the lot in place, most common use is where you can reach under the bowl and get to the wing nut.
The other tends to be a "friction" device where a neoprene expanding fixing holds the lid and seat in place, most common in slow drop seats and lids.
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