Adult size plastic pants are available that will let you sleep through the night with out wetting your mattress. Google will help you find what you are wanting.

I wear them and sleep knowing I may wake up wet, but my mattress is dry.

Plastic pants and a vinyl sheet is what I use. 

There are vinyl mattress pads. Plus the various disposable incontinence pads (chux pads).  What is Your level of incontinence ?  Do You wear a pad or brief (diaper)   All these questions can help answer Your question.