The most popular ones are the Dexcom sensors and then the Freestyle Libre. Unfortunately you need a prescription for both in the US. Otherwise, if you'd like to monitor your blood sugar, you'll have to do it via a blood glucose meter and just space out your testing. You can buy those over the counter at any pharmacy/superstore and they're relatively cheap.

If you end up buying a blood glucose meter, the best way to get a good idea of your blood sugar movement in your body (if there is any) would be testing at several times throughout the day after specific events (like eating and/or exercising). Waking up (for fasting glucose), pre-meal (to get a baseline), post-meal several times (15 minutes, 1 hour, 3 hours). I would also experiment with how it reacts to different types of food and beverages. For example, try drinking a glass of orange juice and testing 5-15 minutes after. Some non-diabetics still experience very small blood sugar spikes from liquid carb sources.