That's how I make a living. If you weren't so damn far away we could trade labor for beer.
I normally pull the vinyl and luan and use 1/2" cement board on the subfloor. Make sure you mortar and screw the 1/4" and you'll be fine. You can use cheap unmodified mortar under the board but get...
I picked up five regulars from two grocery stores near me. They didn't have variants but it seemed like the regular stuff was abundant. If I'd been even slightly motivated to collect a bunch it would not have been a problem.