http://www.modelfixings.co.uk/self_tapping_screws.htm I'm going to try them... I'm going to order a pack of the 0ga/1.5dia, 6.4mm long and a pack of the countersunk 2ga/2.2dia, 6.4mm long and see which one works best. Since I'm having to fill in the holes in the wood anyway, I think I might end up going for the 2ga countersunk as I think the metal bar it goes through has big enough holes for that.

Having to make up the order amount with some UNC 1/4-20 nuts so now I'll have some tripod bushes