Connect a laptop wirelessly to a wired LAN with no router

What are my options for connecting a laptop wirelessly to a workstation that is connected to a wired LAN and has no router? Essentially, I want to add wireless connectivity to the workstation so that the laptop can connect to the wired LAN via the workstation.

Is there a specific reason why you can't add a wireless AP to your LAN?

Not that I'm aware; is a wireless access point the way to go? I'm looking for a cheap option.

I have a wireless USB adapter that I use in another location to connect to a wireless router: could I use that to add wireless connectivity in the situation above?