kinda shocked that the SM7 is not working well for him, but so be it. it's one of THE mics for that kind of thing which is probably why so many people replied with a vote for it. SM57 would be my next try.
if you're using a DAW (or if you can afford a few analog tracks) and you can use a mic stand with him, put ALL mics up that you listed--anything that might work really. then, put a pop filter on a seperate stand and have him sing the same verse on each mic as seperate takes, moving the pop filter down to each mic as he goes along. then, have him go back into the control room and the two of you pick the one that works best. in ten minutes or less, you'll pick the best one and have the rest of them back on the shelf for another day.
btw, i've used the beta58 a whole bunch in the studio on vocals. i love that mic. other circumstances than sound led me to using it, but i still go to it from time to time.
good luck and have fun.
matt