Been using lacquered floor tiles or wall tiles as a source,seem to do the job same thickness.
Punch them out soak them and punch out a centre far better than originals they don't leak.
I've used BAPs for years on Commandos. They're great. I intended to carry one as a spare on the 16H but they are too tall and don't clear the inlet stub on the Norton.
An Enots HexagON is only about 1 5/8" from the tank face to the lower connection. A BAP is 2 1/2" minimum.