Anyplace that sells janitorial supplies for commercial or office cleaning will have a selection of different types of mop heads. Also check the office supply type stores, they carry cleaning stuff for businesses too.
Depending on what wax you are using, on what surface, different types of heads are most effective. A commercial janitorial supply place can tell you which heads to use for what purpose. If you are only doing a small floor (like a kitchen) with the wax you can buy at the grocery store, you can just use a rag or sponge to do it by hand, no full mop required. If you are doing a large space, make sure you are using the right wax for the surface, the wrong wax will make it look worse and you'll probably end up stripping it off and doing it again.