It claims to be BSP, but it’s 1 inch (1.1?) with 19 threads per inch (18?), which matches no standard I’ve ever found.
Print a mold, cast it in wax, put that in casting sand, then do a lost-wax casting in aluminum or something more exotic if necessary and you're able?
I think at that point I'd have to ask someone to make it for me.
Lathe would be the tool to use in that case.
You're absolutely right. But I have a 3D printer, casting sand, and a torch... I don't have a lathe, sadly.
A 3D printed plastic part could be fine depending on the application. Certainly worth considering/testing. Printing it flat on the bed (with a small flat side) so layers are lengthwise may work.
If it needs any amount of strength you'll want to find someone with a lathe. BSP tells me it may be tapered(?) so find someone with a taper attachment. Even as a hobbyist I could probably make one of those on my lathe faster than drawing it and printing it on my 3d printer.
See also threaded inserts for the other half of that fastener.