I use polar fleece from ebay and make liners usung
Fleece, cotton mattress protector, fleece
Fleece, zorb, fleece.
Both work well. Zorb is extra absorbent and more expensive so I now use it in the mats to go under their beds as extra protection!
Having hay trays encourages them to wee mainly in them thus saving the fleece liners from being changed too often.