The filter floss is kinda like cotton stuffing. Most lfs should carry pretty good sized bags of it for like $2 or so. I put it on top on the bio media, and a first it was white, now, it's all brown and I know I need to change it, but I've been pretty bussy.
Yeah, I do think that a coffee can lid w/ holes in it could work, but you're gonna want a wet/dry that's bigger than that. So what I suggest is to look up in the phone book 'plastics' and find one that's near you and ask if they sell acrlyic sheets to the public. They're really cheap, and the acrlyic sheets just come in handy for alot of different stuff, so just worth having some. But anyway talk to someone that works there, and you might want to ask them if they could cut a circle to a specific size if you dont have the tools that you need. Cutting circles out of wood is pretty difficult, but cutting it out of acrlyic is a little harder. You want to cut with the saw and not melt it with the friction produced. So, get a hair drier out to cool it off while your cutting, oh it will smell pretty bad when you cut it, that's normal. So cut it with a jigsaw, that's the easiest way that you could do it. Then you need to get drill, find what size hole you want, I'm not too sure, but the more the better. Make sure that they're evenly distributed throughout. And that's really it. If you have any specfic questions, feel free to ask. I'll probally have to ask my dad when he comes home tom.
-Mark