I'm actually really surprised to hear people ask for a copy of your notes when you haven't offered to share… What nerve they have to copy someone’s hard work! I understand cross-checking notes, asking the occasional question etc, but copying, whoa, I'd feel really uncomfortable asking someone no matter how great their notes are. Haha.
Honestly, help those who you feel comfortable helping, or you feel truly deserve/need your help and stuff them if they're "I don’t have to do my own notes because they I can get a copy of Ghost's notes. Yay!' kind of people.
Maybe you should ask them why they don't have their own notes, or why their own notes aren't sufficient. (In a nice way of course!) Maybe help them make their own if they're not sufficient, for example telling them the relevant pages from the text book, how to set notes out, what not to include etc if you feel more comfortable doing that, you're still being helpful, probably more so because they'll probably learn better writing their own notes.
How to reject nicely? Well with a white lie I think. Just say you left them at home, they're not yours, aren't finished, are illegible so on and so forth. If they get all angry, well their motives but may not be so genuine, so stuff them as well! Hahaha
But yeah, helping your cohort is pretty good idea, pretty worthwhile I believe, but doing the work for them instead of with them, well thats not so good not to mention unfair, and no one should ever be put in this position if they don't want to be, no matter how crappy the cohort is...
Yeah my two cents hahah