Okay, draw up a suitable file, and determine what sort of hardware will be used — M6 is needed for the threaded table, but if you’re in the U.S., 1/4-20 may be more convenient, so making use of both — adjust for your locale / inclinations / OCD.
The clamp will be cut from a bar of aluminum, 1" wide by 1/4" thick is readily sourced in the U.S., and will have two holes, one threaded (for either M6 or 1/4-20 — you pick — the latter needs a #7 drill bit so we draw a hole 0.201" in diameter, while the M6 needs a 5mm hole (0.19865")) — this will accept a suitable bolt — a carriage bolt is an interesting idea, the round head would be less likely to mar the table, or perhaps one could use nylon (check the plumbing supplies — 1/4-20 is the standard size for mounting toilet seats), or one could use an upside down SHCS w/ a plastic thumb nut attached.
The other hole will need to accommodate either an M6 or 1/4-20 bolt and its threads — measuring a pair suggest 5.9mm or 6.2mm, so we round up to 6.35mm (1/4").
Shape the other end suitably and one arrives at:
