If you just want something different, or need a chocolate fix, why not toss some cocoa into your coffee (with a bit extra sweetener, or not)? I have mocha every morning. I’m going to try Montezuma if I ever get by Trader Joe’s again, but I found this “Eating Evolved” bar at Sprouts, right next to the Lily’s Dark Chocolate (my fave,) and it’s possibly available at places like TJ, Natural Grocers, Whole Foods, etc. (NOTE: this is the only thing this brand sells that is keto friendly. Coconut sugar or other stuff in everything else).
Also, maybe 1-to-1 substitution is not realistic. Can you do with a smaller serving? Lily’s bars go on sale occasionally at Sprouts for $3-3.50. I find that 1/4 of one of these bars is more than enough for me (and I used to be a big-time chocoholic). The Midnight Coconut was more, but I bought it out of curiosity more than anything. That’s .75-.80 for a nice piece of chocoate, not too terrible.
There is a really good avocado chocolate pudding recipe around that you could fix up and take with you, as well - made with cocoa, rich and flavorful, plus you get all the nutrition of the avocado.
Convenience foods, especially in a niche market, are always going to be pricey. I hope something you get in this thread will help you out without breaking the bank.