I ride flats and after a couple pedal strikes to my knees and shins, I wear kneepads. I use these. I can pedal all day and not know they're there.
Fox Head Mens Launch D30 Knee Guard https://www.amazon.com/dp/B084DL7YG5/ref=cm_sw_r_cp_apan_glt_fabc_NYCEB809PJEEQ929ZPR0?_encoding=UTF8&psc=1