When I was in college, I got readers by putting up notices on all the dormitory bulletin boards. By the time I got them all up, I usually had more readers than I needed. When I want into the working world, I didn't have bulletin boards anymore, so I put ads in the newspaper. This method also yielded me more readers than I could ever use because with both techniques I swept so widely that I got plenty of opportunities to pick and choose among the candidates myself. I can absolutely guarantee you that, if you place a classified ad in the newspaper, you will have to put an answering machine on your phone line to notify people that you have already filled the position.
People are out there looking for jobs or hoping to earn a little extra money.
You want to find those people. Don't ever make the mistake of under-advertising for a reader. Personally, I would never take a list from a disabled students services office or anywhere else. I want my readers to know that I am the one who found them, that I outline the job, and that I am the one with whom they have to deal. Not only is it easier to control the situation if the reader needs the cash, but it is a lot easier if he or she is your age or younger.