High-calorie snacks while on the job?

I’m 21f and weigh ~101lbs and trying to gain weight (I’m 5’4 but rapidly noticing how thin my legs are and I can’t wear clothes that expose my back because my ribs/spine protrude so much) but one of my big issues is getting enough calories while working. I make pottery so it’s more active than just sitting behind a cash register but I have a hard time finding something A. healthy, B. loaded in calories, and C. doesn’t have tree nuts — I’m deathly allergic. I prefer something I can make too, since that seems to help me enjoy food a lot more, but store bought is totally fine too. I know I could look this up online, but then it’s all those health____.com sites that don’t feel genuine or flip flop on their data. Thanks so much!

Edit: I’m also customer-facing, so can’t be pulling out a meal 🫠