dalattin USB-Powered LED Matrix Panel 2 Pack, 14''×4'' Full Color Big Eye Flex Signs for Windshield, SUVs & Medium Trucks & Taxi - Remote/App Control, Custom Car Sign

These are the exact ones I bought for this build. At the time they were the cheapest option. I've picked up several different sets from different brands and these had the best build quality and they use the best app of all the ones I've tried. https://a.co/d/07XNkmmj