A few of the supplies are unique and may need a bit of explaining before you can find them.
Sectional Frame Kits are halves of picture frames sold in various sizes. You can buy, say, a 10" kit and an 18" kit to make a 10" x 18" frame. They also come in different depths. You want to get the 1"-deep frames normally used for canvases to accommodate your board. If you do a search on the Michael's Crafts web site, you'll find 'em. They're also readily available in most craft and frame stores.
Zinc-Plated Steel Fender Washers are just big flat washers with a hole in the center that also happen to be very conductive to magnets. You can get hordes of these for cheap at home improvement or hardware stores. You'll need a single 1" washer for each 25mm base in your army, a single 1.5" washer for each 40mm base, and about four 1" washers per vehicle. Here's what to look for.
NdFeB Disc Magnets are simply rare-earth magnets. The diameter and thickness listed above fits perfectly into the hollow beneath any GW base without adding any height or wobbliness to your models. These magnets are powerful! If you wish to have less "sticky" models, get a smaller diameter like 0.125". A great place to order these suckers online is Amazing Magnets. Fast shipping, easy-to-use site, and awesome magnets. You can get 100 of code D094B (the magnets's used here) for $15.00.
Compass Cutter Tools are essentially knives mounted on a compass. They cut nice, round circles in foamcore and are very adjustable. You can get 'em at just about any local craft store like Michael's, or search around the web. OLFA makes a nice model complete with extra blades that's relatively cheap.
Plastic Nail-on Glides are nails with plastic footies that will act as legs for the display. This way, you can reach underneath the display with ease to pick it up. Here's an example of the one's we used here.