The filter that you seek is unattainable on wgt. You can peruse players pages, and their friends' pages, and their friend's pages, but you cannot filter a search for unafilliated members.
You should create a forum post in the Country Club Corner announcing, and describing, your club.
You could try searching the community and filter members by Tier. I am sure you will find many unaffialited members that are Hacks to Masters. Obviously, many higher tier players are not in clubs but my bet is more of the lower, and newer, members are not (statistically speaking).
Good luck with your club.