This will cost you a lot of money - best to ask folk at IPA/IPF or BALPA about contacts.
Not always a good thing to prep on one before hand as testers will expect to to behave as per your CV experience. Also they may well do test at same company that you practised at and if you do really well then expect to be asked if you've done the sim before.
I couldn't afford it at the time so went out and bought X Plane - bit like MS Flight Sim but better aerodynamics and handling - works on PCs and Macs - there's an excellent 737-300 and you can fly the profiles the Co. sends you. get's you used to Pitch and power changes and rate of events cf Cessna flying!