I have a couple of TWSBI 580's plus some other pens.

Was interested in getting one more (yes, I know) pen that was a piston filler and was wondering if anyone knew of any (not another TWSBI, I need some more variety) where the section would unscrew so that you could use the snorkel/apparatus from the TWSBI bottle for filling like with the 580's?

Thanks in advance!