Bit like finding the sheep in amongst the goats in Taffy's area
In England you have too many window cleaners to choose from in yellow pages, in Scotland you take the phone off the hook as there will only be probably 3 of you.
Get a card in local shops and supermarkets, don't know where you live but a lot of window cleaners also use Gumtree on the web. Do not know how succesful that is.
Or put leaflets on car windows outside shops.
Or put a sign up along the raod.
Loads of ideas to think about.