Would an epinephrine inhaler work for an allergic reaction if an epipen is not handy?

No. Epinephrine inhaled is still used in severe asthma attacks and it can open the airways but if you are experiencing anaphylaxis only injectable Epinephrine is life-saving.
Might not work. Studies have found that, using an inhaler, it is hard to get enough Epinephrine into the rest of the body to interrupt a serious allergic reaction (anaphylaxis). One study looked at children given over 10 puffs of epi., and did not see much effect on the rest of the body. However, any asthma symptoms would likely be helped. If no Epipen (epinephrine) is available, one can try an inhaler, but it might not work.