Have you measured the actual thickness? Hardboard (Masonite is the brand name) is available in 1/8" and 1/4" thicknesses and it also comes in a temperd version that is very dense and hard. You might have to check with Menard's if you're near one or at a local lumber yard. If you need the thicker size Menard's has 1/4' thick in 2'x4' sheets for about $5. Here's a link: http://www.menards.com/main/bu...=1211521147064542273. They also carry small sheets of the 1/8" size.
Another alternative is medium density fiberboard MDF which is available in thicker sizes, but you might have to buy a 4'x8' sheet.
Good Luck,
Mike A.
