Bulb housing: at Walmart, automotive section, look for Optronics QH-7CC ( like these:
http://www.optronicsinc.com/competition.htm ).
Rear lights: look around your local auto parts store for marker/truck clearance LED lights or add-on LED lights.
To mount to handle bars, Home Depot conduit hangers (like this:
http://www.hardwareandtools.com/invt/6306054 ) You can buy them in different sizes to fit your handbars.
Battery: cheap and the recharger is cheap too: 12v 5 Ahr sealed lead acid
http://www.zbattery.com/B-B-12V-5Ah-...category=60816
You can get a blade fuse hold at any auto parts store. I use a 10 amp fuse in mine.
I use a cheap under-saddle bag from Walmart to hold the battery, fuse, and switch. It isn't the fanciest system, but it works day to day, and is easy to fix and replace worn-out parts.