If you're careful, you can drill a hole into the old terminal, thread it, and add a bolt. I've done that in the past. Battery was old anyway and wasn't going to last much longer. Gotta be careful not to drill to deeply though.
In future, just leave the battery grounds disconnected after servicing and charging the batteries. They'll last all winter without problems. They're good down to -76 F. An older battery probably good down to -40 F.
Come spring, plug in the RV so they get charged up. If your rig does not charge the chassis battery, get a AC operated 1.5 amp float charger for $25 and attach that to it for a few hours. Or you can buy a Trik-L-Start which is designed just for RV chassis batteries and what it does is steal a bit of current from the house batteries to keep the chassis battery charged up.