pooljunkie is spot on with his posting.
For every good midi file out there there's just as equal amount of bad ones. Google will come back with alsorts of sites (some that are nothing to do with what you want) but there are some search engines that specialise in finding midi files and kar files only.
I'm sure someone has posted a link to some search tool on here before but I've no idea what the site was. Maybe someone will read this and post it? It's a case of trial and error, visiting sites and taking pot luck with them.