? How's rising that floor going to effect being able to even get the washer in place under the counter top?
A couple of ideas.
1, Have them lay the flooring until just under the visible area at the front of the washer, then use plywood for the rest of the floor and cover with glued down linoleum.
2, Any real HVAC shop can make you a pan out of galvanized metal in a few min.
If it was mine I'd want a 3 sided pan so if it did leak I'd know it because the water would show at the front of the pan.
PS, wood flooring in a kitchen is not the best idea.