The sizes sound great. I don't know what contact paper is. You might want to look at Ikea - there are a number of units that provide large pieces of melamined wood/woodchip which is already wipe clean.
This for example
https://www.ikea.com/gb/en/products/...-art-30128629/
This (there are a number of tutorials for a Linmon cage)
https://www.ikea.com/gb/en/products/...-spr-29932181/
I've also seen two large lack tables used to make a cage on legs (one table fixed on top of the other - the bottom one provides the base of the cage). Which is a good size. For that you would need sliding doors though.
https://www.ikea.com/gb/en/products/...-art-10065958/