Menards, Home Depot and Lowes all sell sheets of "Formica" (common name for laminate, just like "Sheetrock" is common for gypsum wall-board even though that is a brand name too) . The brands you will find are typically "Formica" and "Wilson-Art" and "Pioneer".
Usually they will have a few select sheets in stock of common styles, and then have tons of hanging tags of samples of sheets you can order.
Warning: It gets VERY expensive to put formica on your cabinet. Unless you built the cabinet out of a single sheet of plywood (most can't get both sides to fit), then you'll need to buy 2 whole sheets of formica and pay a lot for it, especially if special order.
Plus you'll need contact cement and a router with a trim bit.
Honestly, it's cheaper and just as easy to just buy real oak or birch laminated 3/4" MDF sheets to begin with (appx $32 for a 4x8 sheet at Menards when on sale) and then just buy a $5 can of stain and $7 can of polyurathene and stain and poly it in the color you want, and have real hardwood exterior. Farily durable, hides simple scratches well.
That's what I used when I built an Atari cabaret replica. Turned out nice. I primed and spray painted black the cross-pieces at an additional cost of about $5 in paint.