Hi Gabe and Welcome to HealingWell! 
I did a little checking and the only smaller epi pen that I've found is the epi pen jr. for children - I imagine that is due to the fact that they take a smaller dosage of the medication.
Perhaps some others here that have heard about something new will come along and let us both know! 
So please check back, Gabe.
Hugs, Teri