https://community.kidswithfoodallergies.org/blog/what-are-your-options-for-epinephrine-auto-injectors describes the various epinephrine auto injectors, if you want to shop by size/shape for ease of carrying.
You may want to pay attention to peanut desensitization clinical trials and such, which aim to get the patients to the point that the risk from minor cross contamination or peanut dust is lower than it was before.