I couldnt find a spool holder that would fit on my bed, so here is one

print one of each,and 2 of spool bearing, insert skate bearing in bearing holder, 2 off m8 bolt and nuts clamp the holder onto the top bars of the printer, and a length of m8 studding and several nuts clamps the spool to the top. Sorry the orientation of the spool bearing is wrong, spin it 180 deg.