Esp32 cam has storage of pins for external sensors. I have read SD library can be used using 1 bit mode. Is there a nice article on using 1 bit SD in ESP32 and make few pins free
I think this covers what you are looking for: https://www.reddit.com/r/esp32/comments/d71es9/a_breakdown_of_my_experience_trying_to_talk_to_an/
Let me know if this helps.