Don't you hate it when theres a gap in your ring binders when you close it shut. The gap lets the plastic wallets you so carefully organised to fall out and become disordered. I thought of a simple solution to help my brother with this problem- straws.
Get a straw that fits around the metal ring. Put it on the metal rod and cut it 2cm above where the rod ends. Feed the open end of the straw over the other rod that makes up the ring. And carefully close so the straw doesn't get caught in the gap.
Hope this helps.