I designed this adapter / bracket to mount a generic spool holder to my Bambu Lab X1C. I printed it in ABS but other materials should be possible.

You also need:
2x M3x14mm bolt.
2x M6x16mm bolt (or longer: can be maximum 44mm long).

2x M6 nut (press them with a little force in the back of the bracket (I used a longer M6 bolt to do that easy).

The part can be printed without extra support and has a little support tab wich can be breaked away to allow installation without detachning the ptfe tube.