After I went to Walmart, and they happened to have the Franklin Covey planners on clearance, and probably because it is the end of the school year other retailers may have similar clearances. I was able to get a zipper-close leather binder for under $6, and it included a ruler and two pouches, as well as various dividers and pages, most of which I will discard. The significant down-side to this great bargain is the need for a 7-hole punch compatible with the planner system. Franklin-Covey sells a metal one for over $20 that I was not about to buy, especially when I would be punching at most 3 pages at a time! I searched Amazon and found one through a third party vendor that was slim and would fit into the binder itself. I kept one of the sheets to use as a template that I place over our nature sheets and then trace the seven holes with a pencil. I can use a standard hole punch for three folded 28# sheets together by lining up the punch with the drawn circles. A bit labor-intensive but it works.
Amazon has a wide variety of binders including great faux leather journals if you are so inspired. Many of these are 6 ring binders, meaning an investment in hole punch. I could not find any mini 3-hole punches on Amazon but I did find one for around $9 at Staples.