So basically my pc is built but the cheap 750w game max psu I bought used for $20 bucks is missing all its modular cable’s especially the ones that power the gpu which I didn’t bother check until my pc was built.

Leaving me with 3 options

Option 1: get the missing gpu 8pin cable which I dont know exactly what model I would need for a gamemax 750w gpu or if I can use any random 8pin cable

Option 2: got a friend selling me his 850 Corsair rm850x for $100 bucks

Option 3: got someone else selling me their used cx600 Corsair for $30 but its a really old model and i dont if that’s a good idea

The psu would be for an Rtx 3070 and Ryzen 5600x

What would the veteran pc builders recommend I do?