Go forth to the Fred Miranda macro forum and look at the "show off your kit" thread that stays at the top of the forum. You will find every possible variation on close-to-lens flash mounts, from commercial macro mounts like the MT-24EX to home-made items of all descriptions. One of the easier ones for hand-held work is to swing your tripod ring so that the foot is pointing up, and mounting your flash directly onto the 1/4-20 socket on the ring foot.