In reality you could use just about any mic for this application. Many people will use a small diaphragm condenser mic such as a Shure SM81 or equivalent. If you're looking to get more low end response you may want to try a large diaphragm mic though I find that my artists seem to like them high passed quite a bit. I've used everything from 57s to expensive Neumanns with the same modus operandi: make it work.
A good simple starting setup would be to set a mic on each side of the stage on top of the side fills, pointing a bit down towards the audience. Make sure you tape them down so they don't vibrate away. If you can access the truss you can do a pair in the center in a "V" shape, again pointing a bit down towards the audience. In many cases that may put them too far away but you never know until you try it. In either case it seems to work better if you don't pan the mics too wide, perhaps around 9 and 3 o'clock at the widest. YMMV.
It's also usually a good precaution to limit the ambient mics as they go to the IEMs since crowds can be extremely dynamic and you wouldn't want to blow out an artist's eardrums if they start screaming.
