You can pick up a set of roller blade pads at Target or Walmart for like 10 bucks that have knee pads, elbow pads, and wrist wraps with hard plastic palm guards on them. They usually stock 3 sizes. Really small like your child would wear, a bigger set for older kids, and an adult set. My daughter got her set on her own this week when she tried out her first 26" bike. She even wore the wrist guards the rest of the day on the trail on the 20". They work very well and after a while, theyll forget all about having them on.
I got Fox pads in the "Peewee" size for my kids. They began wearing them at 3 years old (My daughter is scrawny too). The knees are better than the elbows. I find the cheap knee pads just slide off when they fall, and the Fox ones weren't too much money. I was able to order them online. Hope this helps.
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