If I were you, I would get two crates and leave one at work and leave one at home. I prefer the wire crates. If you really really only want to have one, I would suggest a travel vari kennel because they are MUCH easier to transport than the wire kennels. Here's a travel vari kennel that would be easy to transport from home to work. If you yorkie doesn't have a problem wtih going to the bathroom in the crate, you can also get one side up...but make sure that's only if s/he doesn't have a problem wtih going to the bathroom in the crate, in which case you would need to get the smallest one possible:
Petmate Fashion Series Kennel Cab - Intermediate - Carriers - Dog - PetSmart