How to find small cap ETFs do a small part of my portfolio. Obviously aggressive and risky but want to put a small percentage towards this

I am 32 years old. Going for retirement. Gonna put money into VOO, SCHD, and QQQM. But wanna put a small percentage into a small cap ETF as well and want any advice on how you would pick which one. I use Webull and they don’t have a good screener. I was thinking small cap S&P600 but not set in stone yet.