I never use 12X12 in a batrhroom. Moisture can get between the joints.
In a small room like this, sheet vinyl is a doable DIY project. Avoid the 6X9 remnants at the home store. Get a top of the line like Solarian. Get the type that does not require complete glue down, only around the edges. Get the 6" width. 2 yards should be under $100
Be sure to go over EVERY staple with a 4' broad knife. If you feel or hear any 'click' then it is not set deep enough. Then you must spackle over each staple and all joints with something like QwikFix.
Have you considered ceramic tile?