I guess there is a lot of part snobbery here. I don't see why one can't use some bland piece of metal with a threaded hole ground to size and screwed to the chassis using a small spacer (or a shim) if chassis flex is a concern (which I don't think it should be). Or just a screw with a nut and a number of oversize washers. Much easier to tune as well by adding or taking away washers. Or just good ol' wheel balancing weights with double sided tape.
Of course this is not going to increase sales of nicknacks from major manufacturers at overinflated prices.