Hi Ron - thanks for that. I'm trying to source some locally, hence the question.
This virus thing has clobbered our local economy even further, so a few things: Exchange rate is chronic, postage costs have become insane, I don't think our post office is functioning yet (when they do, the backlog will take months to clear...), and at the moment it seems as though eBay is shut down to SA buyers anyway.
I measured 22tpi, so that fits in with the BSF that you provided at 5/16" - many thanks for once again coming to my rescue!!!