Hi Sal,
I have adapters in most thread sizes. The 8mm tube usually takes M14 x 1.5, the 10mm tube usually takes M16 x 1.5.
I would like to see this original black tube that is breaking up. I will pay you to send it to me or swap for something you need.
I wonder if this is really Polyamide or a black version of the 74 White Nylon tube that has a history of being brittle and breaking up into pieces.
Len