Shane,
Try going on eBay. There's a ton of militaria from all periods for sale in their online auctions. Second World War period USGI uniforms and equipment are probably the most represented and there are usually a couple of tanker helmets for sale. Depending upon the quality of photos, eBay can be a descent and cheap reference for military hobbyists. And if you are a collector you may pickup a deal or two.
Goodluck,
Dave