Cherry shrimp are cheap. The problem is that cherry or CRS and to some extent even ghost shrimp need high water quality. 1 gal isn't enough water to prevent large swings in water quality because the volume is so small.
The issue is the volume of water. 1 gal of water will not be stable because it takes such a small amount of waste to effect the water quality. Large aquariums have naturally more stable water parameters. The temp of a 1 gallon tank would move quickly with whatever the outside temp is. A heater would just heat the small oamount of water very quickly and then it would cool quickly, like a yo-yo.
I keep ghost shrimp in a 2.5 gal unheated with a small filter that runs on an airpump (those carbon/sponge combos that cost like 6 bucks). Ive had up to 10 in the 2.5 gal that way for a time and they were fine. We change the water on the 2.5s occaisionally when the bottom looks dirty but try to keep feeding to a minimum.
If you can find them go with a CRS or two but otherwise I think you would be fine with 2 or 3 RCS as long as you are willing to remove the babies if you happen to get any male and female mix. Bumblebees are really nice too...
I have kept 5 Ghost shrimp in a 2 gallon tank with a betta without problem before.