There was a dude over on APC that did this. It's kind of become an inside joke. He blows up like three trash bags using his own breath, and then uses an air pump to pump the bags into his tank. He has to refil the bags every day, but it works. It's a lot of effort, but that's all him.
I say you need to ditch the original hood and get or make a glass or plastic top. With a 10g it is the only way to get enough light on there. I only have 3 12 watt CFLs each in there own fixture. I found that link http://www.qsl.net/w2wdx/aquaria/diyco2.html and I went with a power head diffuser. My plants kick and I can't grow algae except green spot(only in a couple of places)