Need to identify and replace this unknown toilet flush valve seal

[Alsno]

Hi all, I need help finding a replacement seal for a toilet flush valve.
I'm not a DIYer and I've finally gotten round to looking at it after about a year...

The seal has bubbled on both sides, so when I turned it over it is still leaking.

I bought a replacement seal from Wickes, thinking they were universal that it would be a straight swap (but no it wasn't).

It is not a branded flush valve so I don't know what is compatible or what to replace it with.

The dimensions are 65mm (outer diameter) and 40mm (inner diameter). It is 2mm thick and is flat.

I've taken photos and hope someone can help me identify the brand and/or a suitable replacement?

Thanks all

 

[footprints]

Try here, click on washers for sizes.
https://shop.lunns.net/index.asp?function=search

 

[CBW]

Or here, cheaper then Lunns and possibly more helpful. Could email them that photo, or replace the flush valve for branded type?