There are several mini-fridges online in the $50 to $150 price range. They are thermoelectric, and they don't rely on a compressed refrigerant. They're not super precise, but if you live in a warmer climate, it might give you a bit of an edge with your fermentation temperature.

I have two of these mini-fridges. My Cooluli 20L allows me to control the temperature to a fairly precise temperature of up to plus or minus 40 degrees from ambient temperature. It easily holds two 2-quart mason jars with fermentation lids.

The other is a Frigidaire Retro 12/9, which has a fixed temperature of about 15 degrees below ambient (in practice), which should be good enough for fermenting. It only holds one 2-quart mason jar, with enough room for maybe another pint jar, but not another quart jar.. It does not allow you to adjust to a precise temperature, but It's about $100 cheaper than the Cooluli 20L.

I'd rather not shill for one brand or variety over another, but there are options for you to experiment with if you want your kimchi to ferment at mid-range temperatures, i.e. somewhere between the 40 degrees in your fridge and room temperature.

After some experimentation, I tend to use the cheaper smaller unit for fermenting, and then I can use the larger one for storing onions, potatoes, avocados, bananas and the like at adjustable temperatures for that kind of produce. But it's also a good standby if I have a lot of stuff to ferment.

I've only had these mini-fridges a few months, so I don't know how reliable they are over the long term. If they continue to be reliable, they will be a good investment, compared to the cost of store-bought kimchi. Not to mention being able to tweak the ingredients to your liking.

Thanks to Nourished Kitchen for this recipe. It has sparked a lot of jioy, as they say, so highly recommended.