Sure. The best online retailer for this sort of thing is Historical Board Gaming. go there and you will find every piece to almost every AA board game, even some Anniversary pieces. Of course, Ebay is a good way to acquire pieces as well.
I saw your post sitting so long I registered to give you a few pointers on maps. Most if not all the WotC map packs are themed in some way. Originally they were 2" hexes but were changed some time ago. The map packs you mentioned are themed as follows: North Africa - 3 Desert maps and on reverse side 3 jungle maps. Eastern Front - 3 town/factory maps and on the reverse side 3 Russian steppes maps. There are two starters, the one in the cardboard box is the old one and contains 12mm mini’s and 2" hex maps. the new starter is in a blister pack and has 15mm mini’s and 3" hex maps. The maps in the new starter are mixed forest/hills/clear. The rules and revised cards are downloadable through the WotC site.
I have been taking a MK IV basically as bait, 3 machine guns, panzerfaust, some troops, light mortars and two officers. Clearing disruptions every turn is huge. Machine guns work on the troops along with the mortars and the MK IV hopefully holds its own if not the panzerfaust go to work.