Hopefully, you could find a similar (upholstery edge trim) on this link: https://www.amazon.co.uk/Edge-Trim-Black-per-metre/dp/B008FQ5BVY

Looks like door edge guard maybe.

I’ve seen that before I replaced it with hydem. But the original closest thing I’ve seen is PLASTIC INSERT WIRE-ON. You usually see that on older mustang rear bow trim or wire-on.

I would use hidem banding or something like this https://www.vintagecarparts.co.uk/parts_index/aluminium-strip

Vintage car parts must have the worst website ever.