I know Ikea has one loft that comes in full size? I don't know if that's enough..
But also, I'd advise against getting one if you're afraid of spiders. I made this mistake recently, and.. eshk. I now have to have magazines and books in my bed with me so I can smash any spiders. But I swear, if there was a big spider, I'd flip out and jump out of bed. Which wouldn't be good, seeing as my ceiling is about a foot above me when I'm lying down in the bed and the bed is like 5 feet high..
Just warning ya.. heh