Here are 2 hard cardboard 3-ring binders from GE Entertainment. Both are classic. The left has pixelated graphics for Green Hill, with Sonic running past a Buzz Bomber who is shooting an energy ball. The other has the neo-classic stock art for Sonic, Tails & Knuckles on the back, with a big Sonic portrait on the front. It has a fading checkers background on all sides. Where can you get these?

NOTE: These are "Hard Card Binders" but they are still JUST cardboard. They dent easily, get bent corners, & can show wear quickly. For something 10 dollars and up, you'll likely want to consider these for HOME use only so they don't get ruined. Store your Sonic trading cards, archive your art, but keep 'em on a shelf.