My best method for collecting pumps in my area (my collection has grown from 1 pump 3 years ago too 9 currently, unrestored of course) has been to approach farmers or persons you know may have collectibles stowed away and just be honest. Strike up a conversation and plan on listening to a few stories, which is always fun and informative in my book. You will also be amazed in some situations where this one person may know of two other people or farmers with pumps!
The key I believe is to just be honest and respectful and you may just get a tour of the old barn on the back 40 shoved full of goodies!!