Got the wife to get me a rather cheap macro flash (Opteka rl-600) to play with. Heads are either left or right or both on but to my suprise they also rotate so you can angle them in,straight or out facing. Seems to work ok but the size of the head and the amount it protrudes forward of the lens end would make it unsuitable for high mag MPE-65 shots I think. Only been able to play with it with the MPE-65 at lowish mags as I need to get a 55mm to 58mm stepup ring to get it to fit my Tamron 90 (it comes with a 52mm and 58mm couplers)- all for £70. First 3 shots taken using it.
more details here http://opteka.com/rl600.aspx
Last 3 shots were taken with a 4X microscope lens my son gave me, I just replaced the 10X lens I had been using on my my extensiontube/microscope lens setup. First shot is a single shot of a springtail and the others are small focus stacks of the same orchid I was using for the flash shots.