Messed up my rear shock and I’m looking into buying a new one

Hello, I was rebuilding my rear shock and cut the piston rod too much and bleeding the shock was super stiff. I talked to a mechanic and he said it could’ve been one thing but since I cut the end of the piston rod too much it’s ruined (there’s a little circle at the top that your not supposed to grind off). I’m looking into buying one off eBay but my bike isn’t that old it’s a 2018 drz-400S and I was wondering if anyone knows of a way to verify if the ones on eBay will fit my bike normally and work well off-road? I was told of a website to find the part number and see if there’s a difference but I can’t find the website or anything to compare the rear shocks. Does anyone know how to do this?