3PCS M4 Hook & Eye Turnbuckle 304 Stainless Steel Turnbuckle Wire Rope Tension Heavy Duty Turnbuckles for Cable Railing Wire Rope Hardware Kit

These would work fine. They are m4 threaded. Normally turnbuckles should have a jam but on each side, but these don't. I would buy a couple m4 nuts and unscrew each side, thread a nut on and then screw them back in and you will have a jam nut to lock them in the length you set them to https://a.co/d/0jh2MeLv