Ebay? For wood? Are you for real? Where do you live, New York City?
Go to any Lowes, Home Depot, builder supply store, lumberyard, etc. They all sell MDF, wood in boards, etc. Some will cut to order, some not. My local lumberyard only sells full-size sheets. Lowes and Homedepot will cut to order. Besides being less expensive than I bet eBay would be, you get to see what you are buying.
"It ain't what you're told, it's what you know." - Granny Weatherwax
Gather the villagers, pitchforks, and torches; we march at dusk!
Life may not be the party we hoped for, but while we're here we might as well dance.