Its pretty easy to measure and jump on a site to find something close. You can not just " screw them " into the side rails though unless only wanting it for looks.
Plus be careful of a lot of cross bars , due to being so high that the basket ends up 6 inches above the roof
Also the siderails are not straight, they are wider in front tampering down in the back
Have exact measurements somewhere here but someone will chime in before I find them LOL
I drilled my siderails years ago for my first setup, ran all thread ( one half inch ) clear across inside of steel pipe, kept rack low and worked for me