I am looking for an original Fig Forth 6502 Source File adapted for the C64.There are some Fig Forth systems without sources and of course Forth systems with sources (Durex, HES Forth, ... https://commodore.software/downloads/category/188-forth) unfortunately they are not as close to the Fig Forth as I would like.
What I need is an adaptation to the C64 (IO & memory, access to floppy disks is not necessary) that also works. I have already tried to port it myself, unfortunately it does not run reliably.
Any hint is helpful. Thx!

ProForth for the Apple is fully FigForth compliant as well as '79 Forth compliant and should work on any 6502 with minor changes. With an Apple II emulator, you might be able to transfer the binary over to a .64 disk image. I can read and write to .64 image on my end, if that helps.

Or if you would rather have a source listing, let me know.

Thank you, however I have the original Fig Forth sources in the Apple II version (e.g. -> https://dwheeler.com/6502/ ). What I am looking for is adapted Fig Forth version for the C64.