I just received a Key Lime Tree about 2 1/2 feet tall as a present. I live in an apartment with windows that will only allow about 4 hours top of direct sun light each day and don't have anywhere to place it outside in the summertime. Clearly artifical lighting is the only option I have right now. My question is where do I go from here, in terms of proper lights?

On a side note I can't hang anything from my ceiling and don't have the room for an elaberate setup.

Here are some pictures of my tree and the space that it's in.