I don't think anyone makes face plates that will fit the Avon anymore. Even secondhand you might have to wait a long time to find one, most get sold complete with the lathes as people trade up.
As others have said, your best option is buy a chuck with standard jaws and get a faceplate ring that fits onto the chuck jaws. You'll find a chuck invaluable anyway. You have a choice of three* that are available with inserts to fit the Avon, the Toolpost Versachuck, Record Power SC4 and Sorby Patriot. Any of these will be a good investment as if you need to upgrade in future you'll only need a new (cheap) insert to fit another lathe.
My Avon has both ends with MT2
A final note; Check that the thread actually is 25mm x 2mm before buying anything. Tyme also advertised it being available with a 3/4" 16tpi headstock too.
*It's also possible to get the magnificent Axminster SK114 in the correct thread, but it's expensive and doesn't have interchangeable inserts if you need to upgrade.