Thanks for the quick responses!!
As for Henry Cowell's music (and for that matter, Lejsek's) I know that stuff is probably not going to be in the public domain, so I don't necessarily need a free copy of it, I'm willing to purchase it if its in print by any publisher.
Thats the thing, is that I can't find any sort of publishers that have the rights to any sort of obscure 20th century composer. I mean, the only thing I've found by Lejsek was a publisher named "V i V o - BRNO", which is Czech, but I can't find a publisher's website to order the music directly from them, or anything like that.