For Mags, definitely head south on 28 through Manassas to Virginia Arms. Decent selection of cleaning supplies, but I've never seen ballistol and never looked for eezox. It usually has a good consignment selection for guns, too.
In addition to the regular shops, the NRA range in Fairfax is a good source for ammo. They normally have some of almost everything on hand.
I don't know what their limit is, but you should be able to find what you are looking for. They also have have 9mm and 40 sw glock mags from time to time, always seem to have 8 rd chip mccormack mags and between the range shop and museum shop, they have a decent selection of cleaning gear (basic).