Search this site for a rather recent post on this subject. I found a number of sites selling either kits or just the hardware. Others chimed in with more suggestions.
Are you renting or buying? Your landlord may have a lack of willingness to let you build a Murphy Bed into wall structure? And it sounds like this is temporary so are you sure you want to expend the funds? If you build it in, your landlord may be even more resistant to the idea of you taking it with you when you leave.
A folded out Murphy Bed is still going to take floor space when folded out so you cannot put anything it the space. How about a nice futon or sleeper sofa you could take with you or sell when done? They come in handy for permanent home offices, guest rooms, etc. You can get really nice mattresses for them these days. You can get frames in sizes from twin to Queen and even King I think.
Affordable Portables is a popular place here. Their website will give you some ideas. Overstock and even Amazon would also have ideas. Ikea too I guess.