What kind of theme are you using it for?
Because that does make quite some difference.
If you want to portray the workings of the inside of a hospital or clinic - you got to go right deep into the heart of the action.
But if you just want the facade, then just walk right up to your nearest freindly neighbourhood GP, stand outside the big sign of his clinic and shoot your model there lor...
BTW, The Clinic, the bar at Clarke Quay, looks fashionable-nish. But can't make it lah - if you really need more authentic looking stuffs.
Just my humble opinion.
Your best bet is a close friend who owns a surgical practice of some sort. I don't think most institutions would allow such shoots to take place in their facilities. A possibility is to approach schools or private companies with labs. A long shot perhaps.