Fireplace babyproofing

I'm accepting any recommendations. I have 2 fireplaces, one at my house - 12 feet long overall, not sharp edges but brick. Other fireplace is at my parents and it's two steps of granite, impossible to block off because it's the center of the house in an open concept kind of way. I'm not handy enough to make my own...don't want to spend a ton of money if I dont need to (one foam mat thing I saw was over 100$ and we would need 4 of them lol) So! Premade bumpers? Pool noodles? Bicycle helmet for the kid?