The Chinese pen manufacturer Hero makes a ripoff of the Parker 51. These are available over e-bay for prices that are less than most pen kits. I suppose that it might be possible to engineer an approach to redressing these pens with custom turning.
But there are some things to be aware of. The greatest obstacle is that the Parker 51 had a plastic body and a metal slip-on cap that flits over the section. Turning a shop-made version of this combination might present some challenges.
Second, the 51 is a fountain pen with a hooded nib, and the hood is actually part of the section. That's probably ot a show stopper, but it does complicate the cap issue mentioned above.
Third, the 51 employed the 'aeromatic' filling system. That probably wouldn't present a problem to turners, but it is something that some pen users might not care for. And as the proud (?) owner of a few Hero 329's, I have to report that the Chinese version of the aeromatic doesn't work nearly as well as the original Parker version (I have an original Parker 45 that has the same filling system).
