I scratched it in a vice while cleaning it.
At this point I might as well try to find a new one.
Mini spares .
Sommerfield mini
Mini sport
Moss all out of stock.
By the way is this rivet part of the oil gallery's ?
Even another used one would be fine - they are all the same, except for the ones from the Engines fitted to Automatic Gearboxes and it's not something that normally wears out.
The Rivet is a Plug in the Block. Where that one is is for an 'Air' Bleed Relief on the back of the Oil Pressure Relief Valve, so that as that Valve comes off it's Seat, The 'Air' (or Air / Oil mix) on the Spring side of the Valve has somewhere to go.
It's not a bad idea to remove it for cleaning.
I use Screwed Plugs when replacing them, so it makes cleaning again later easy, they don't fall out and they don't leak.
Be careful though when replacing it that what ever you use doesn't go in too deep or it will block off this vent and your Oil Pressure will be sky high.