1st Build, Second machine

[m_c]

If I've worked it out right, all that's needed is a bit angle, with four holes on one side for bolting to the cross brace, then on the other side a big hole (21.5mm) for the anti-backlash nut to pass through, with another two holes for bolting the nut on via the flange (having looked at the dumpsterCNC site, I'm guessing you're for the 25mm cut-down flange option?).
Something suitable could be made with a pillar drill, a couple drill bits, and a hole saw.

Regarding mounting the nut, I'd use a couple nyloc nuts with plain washers to spread the load. I'd also put the bolts through from the alloy side, tighten them into the flange, then use the nylocs to make sure the bolts can't move.

[Jonathan]

Something suitable could be made with a pillar drill, a couple drill bits, and a hole saw.

Yes, I was thinking that so thought there must be more to it.