If you have city water, you might look into one of these:
https://www.supplyhouse.com/Liberty-Pumps-SJ10-SumpJet-Water-Powered-Sump-Pump-Back-Up-Emergency-System
Of course, if you have a well, it won’t help in a power outage.
You have a gamble to take. You’re leaving in 2 years and don’t want to spend. I get that. How often do you lose power, and is normally in rain storms… is one dimension. Another is leaving the wife at home for the better part of year. In that case you ordinarily want full fail safe automated power restoration, not just for the sump pumps. Water damage is a nightmare but so is a phone call from the wife in panic mode and you’re half a country away. BTDT.