Hi Mike,
I'd give the following a shot to start:
http://www.stamford-consultants.com/
http://www.swisslinx.com/
http://www.harveynash.com/ch/
http://www.mbainternational.com/

And Michael Page (you have a contact there )

If you check jobsites like http://www.jobs.ch you'll see that many companies do hire direct from the labour market.