I am a veteran of potty training. So you can trust me on this. The Bemis Next Step toilet seat is simply the best toilet seat for potty training. You can pick it up at Home Depot for $55.98.
This toilet seat works for both children and adults. Toddlers are happy to use the child-size seat without fear of falling in and I am happy to not clean up the mess made with a separate potty seat. The adult seat includes a soft close feature which prevents both the ring and cover from slamming on little fingers. And best of all the seat includes a special hinge to remove the seat for easy cleaning.
I am about to embark on another round of potty training adventures. Bring on the hand sanitizer, mini M&Ms for rewards, 846 pairs of pint-sized underwear and an unlimited supply of wine for me.