Have you tried nail polish remover?
I do a xerox transfer project with my seniors - basically I have a one page
handout full of a variety of clip art images I have found - we cut out what
we want to use, and then place face down onto paper, and rub nail polish
remover onto the back - the xerox tranfers quite well.
Different papers react differently of course - some are better than others.
The photocopy has to be heavy ink, and a lazer image (not ink jet)
Also, the nail polish remover has to be acetone (not the non-acetone stuff).
I usually get the lemon smelling stuff - hahaha!