get some tubular nylon webbing should cost around $1.00 per yard. Slice it open for the majority of the length, say - 35 inches for a 42 inch waist. Get some buckles from REI and a flat coil zipper from a yard-goods store. Heat seal the cut edges of the tubing with an iron or open flame (depending upon skill and daring - make your choice - I don't dare to melt nylon with my wifes iron....:)), Sew the zipper into the opened length of the tube, attach the buckle and fill with your favorite survival supplies.

My main concern when I looked at this kit was all the lumps in the belt poking against my hip-bones making my belt uncomfortable. I suppose it is all in the packing technique.