Need a link to buy disc brake kit

SuperATV rancher kit will fit the 300 fine,

https://www.superatv.com/honda-rancher-front-disc-brake-kit

or use Shadetree's link and get the HL. I wouldn't get the offbrand/ quadrax or whatever it's called. Guy here that I deal with tried one and set the calipers crap and bleeders stripped out easily ruining them.

All the same. Don't even know why they list them for separate models.

If you look at the brake backing plates 350 rancher, 650 Rincon, 500 Rubicon (01-04) 400 and 450 Foreman, 400AT Rancher....all the same backing plate. That means that brake conversion bolt pattern will fit all of those AND the 300.