Hi. I'm actually trying to accomplish the same goal. It depends much on how accurate you want to be and how much money you're willing to spend. No matter which way you choose though, I'd recommend using actual skate boots since normal tennis shoes don't give enough support to prevent you from hurting your ankles.
Option 1- Just take the two wheels off the middle of a skate and shave the middle of the chassis. Cover the sides with a painted paper mache shell or wonderflex.
Option 2- Get a normal skate and remove the entire chassis. Then, buy a c-channel aluminum bar with the proper dimensions (depends on what size wheels you want) and cut the bar to a proper length. Next, drill holes in the bar where you want your wheel axles to go. Finally, attach the wheels and cover the skate with paper mache or plastic to make it look like an AT. This method probably takes the most time and is a bit more difficult, but is the most accurate.
Option 3- Buy a set of speed/ racing inline skates with 5 wheels per skate. The second and fourth wheels will be in perfect placement to resemble an AT, so just remove the extra wheels and shave off excess chassis. You can be very accurate with this, but racing skates are at least $120-$150 minimum unless you can find them on eBay or something.
Option 4- Buy a set of normal inline skates and remove the chassis. Also, buy "caster wheels" (aka shopping cart-style wheels) off the internet or local Lowes. Then, epoxy/screw the wheels onto the frame and cover with paper mache/wonderflex to make the asthetics.
Anyone else got any ideas?