5 dollar timer. Cycle the refrigerator on one hour and off for maybe 4 hours. It's not going to be super precise, but, imo, curing isn't sous vide- you're replicating a cellar environment and while cellar temps tend to be relatively stable, they fluctuate a bit. For 5 bucks, it's worth trying.
Edit: https://www.amazon.com/dp/B07F6XJXBB/ref=dp_prsubs_2
This will go down to 1 minute intervals. 1 minute will damage the compressor, but there will be a setting low enough to keep the temperature relatively stable that doesn't damage the refrigerator. 10, maybe 20 minutes might be a happy place.