Frozen vegetables are pretty cheap and easy to warm up quickly in the microwave or an air fryer. They may not be as good for you as fresh produce, but that can be a reasonable tradeoff based on the season and free time.
Chest freezers are reasonably cheap to buy (new or used) and cheap to operate, assuming you have the physical space and an open electrical outlet. They don't consume much electricity, mine uses about 75W for the compressor (when it's running, which is less than 50% of the time) and about 250W for the defrost heaters (which seem to turn on for about 15 minutes roughly once per day.