I got it on Amazon https://www.amazon.com/dp/B000H8BU5Y/ref=cm_sw_r_cp_apa_i_rCUDDbW7EKXKJ
It's an ok lock. With my bed cover it really just prevents crimes of convenience. I'm actually thinking I'll just replace the handle with another plastic one, since a metal handle might break the lock if someone got enough leverage
I got the pop lock. Pop & Lock PL2310 Black Manual Tailgate Lock for Mazda/Ford (Works only with factory plastic handle) https://www.amazon.com/dp/B000H8BU5Y/ref=cm_sw_r_cp_awd_x8U6wbMCK5V3A
It wasn't that expensive when I got it. But it works fine.
https://smile.amazon.com/gp/product/B000H8BU5Y/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
This is what I used when I wanted this feature.