http://www.festo.com/INetDomino/coorp_sites/en/c4685b7b78c074c7c1256b87005726fa.htm
I don't have time now for detailed search, but have a look at here. festo is related with hydroulic-pnomatic automation, but maybe you can find something.
I think this will help you.
www.traceparts.com
they have a demo cd for a month...you can download or order it. but as you mentioned, although they are not in STEP models, but PRO-E parts, there is no model tree and no modification is available. at least for the mechanical components (like...