Check the packages carefully for what the sweetener is. I know for a fact that both Hershey's and Russell Stover use malitol, a common sugar-free sweetener in processed chocolates and candies. It's also a known cause of explosive diarrhea. I won't even touch the stuff, but maybe you can handle it.
Most of the other sugar-free sweets use asparatame. A few use Splenda. If you're really--really--lucky, you can find chocolate sweetened with less harmful sweetners. Swerve makes chocolate bake mixes, sweetened with erythritol. I think they have a chocolate cake, brownies, and some cookies. They're gluten-free, too, although they use almond flour. So beware if you have a nut allergy.
A brand that has stevia-sweetened chocolate is Lily's. It's not all that great of chocolate, but if you're desperate, I suppose it would do. Don't laugh, but Lakanto has monkfruit-sweetened dark chocolate chips, like what go into cookies. I eat them out of the bag like candy when I'm desperate for chocolate candy, LOL.
I've found some vegan (non-dairy) ice creams that use stevia, monkfruit or allulose. So Delicious has a chocolate variety that uses monkfruit with eryhtritol. It's pretty good. Amazon and Whole Foods also carry similar desserts. Also, check your local supermarket as well. Many of the bigger chain stores out there are coming up with their own vegan sugar free "ice creams." My stepsister swears by Higher Harvest from HEB. If I lived in Texas, I'd try them, too, because they're vegan and sweetened with monkfruit, so they're only 10 or so carbs. Per pint, not serving.
I'm also lucky that, although it's a "normal" sweetener, agave tends to agree with my blood sugar, and I'm not alone in that. Many diabetics process it quite well. Maybe you're one of the lucky ones, too. Nadamoo is the brand to look for if you're interested in agave-sweetened vegan yum. Their ice cream is just like the real thing, and the taste is OMG out of this world good. The chocolate is especially decadent.
Beyond that, you can get "creative" with Truwhip. It's basically a keto Cool Whip sweetened with monkfruit and allulose, one of the new sweeteners out there. Anyway, to turn that into a chocolate yum-fest, just add some cocoa powder, vanilla and liquid stevia or monkfruit to taste. I've also added a bit of espresso powder and vegan cream cheese (VIOLIFE FTW!) to give it some oomph. A whirl in the Cuisinart will get it all mixed up just right. If you get the right balance of ingredients, it turns out like chocolate mousse.
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