I agree with Aaron; making your own washes is both easy and cheaper.
Les Bursley of "AwesomePaintJob" has a nice tutorial up on you-tube:
But you can probably mess around and find what works for you quite simply.
Basically, you just need some clean water, pigment (paint or ink) and acrylic medium (matte, satin or gloss). Everything else you add to the wash mix is just bells and whistles!
Oh, and do remember to write down what you mix as you go, since you might want to re-create it at a later date. Getting a match between different batches is dead easy if you have the recipe scribbled down.