Heiko,
While I don't know of any commercially-available press, there has been
discussion on this list-server about what you need from a paper where
the investigators mounted two hot-plates (one inverted...) in a
hydraulic press. I didn't save the reference, but you should be able to
find it in the archives. Depending on the polymer and your application,
you may not be able to get enough thermal conductance for a strong
bond, but as I recall the paper said it was  a successful technique.

Regards,
Philip D. Hewes
Department of Biomedical Engineering (Undergraduate)
University of Michigan: School of Engineering