Can't say that I have.
take o picture of what it came out of. I have seen a flapper with pins similar to that but it has a counter water bucket on the opposite end. small cup would hold water and drain out of a hole to let the flapper stay open a bit longer. It had pins that went in divot holes on flush valve in stead of clipping onto bars protruding from flush valve. Look for a KORKY flapper. the have a ring that will slide over the overflow tube for those flush valve that don't have the bars sticking out.
Replace the flush valve for one that takes a std. flapper. Also the flapper may not be your problem. It looks like the refill tube is down into the overflow below the water level in the tank. Causing the water to siphon out of the tank.
The Korky fill valves come with a little clip that keeps the tube above the overflow. I do believe I see it in that picture, so I don't thing it's siphoning.
Korky also makes a universal flapper that should fit that application. It would slide down snugly over the overflow tube.
If you need an exact match without all of the work of changing the flush valve, maybe you can find help for your Mancesa toilet at Ceralux.
1.888.CERALUX(237.2589)
It's worth a shot, right?