Spark plug lead boots for cam cover

I’ve two cam covers, a Novamotor and an England, both require boots to enclose the lead holes. Does anyone know of a source?
This is the England, it’s magnesium and made by an Australian engine builder in the 60’s

Scott’s Old Auto Rubber in Melbourne might have something that would work or could be adapted.

Thanks David I’ll drop them an email with dimensions. I’m trying to remember if an old Toyota or Carson engine had deep Spark plugs and had rubber covers
V