The 72v-12v 10a one is what I got. You can find it under the bike, just above the motor. You'll have to pull the bash guard off to find it. I'm about to hit the sack, but there's a video on YouTube explaining how it all gets wired. I'll link it when I can. If Reddit kills the link you can search "HOMELYLIFE DC 72V Step Down to 12V 10A 120W Voltage Regulator" on Amazon.
This is the one I use: https://smile.amazon.com/gp/product/B089LVTBBL/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I have an extra one brand-new lying around I'd be willing to part with for $20 shipped if you're interested? I'm not sure if the one you posted would fit under the bash guard, but this one definitely would