Find full-sized images

I have a collection of about 2,300 thumbnail images (about 120x180px) and I'd like to find the full-sized versions of them (about 900 x 1280px). I have tried various reverse image sites (google, yandex, tineye) to no avail. The images are dated from around 2004-2006 and they are legal. If there was any copyright associated with them, I cannot find it and regardless I imagine it would have expired by now.

I am willing to pay 25c per full-sized image found. The full-sized images must be sharp - not smaller images blown up to a larger size.