python,

not sure how small your head is but mine is pretty small as well. often i can't find hats to fit me even if they are "small." i think my head is like a size 6 and 3/4 or so if that helps.

anyone, trying on different helmets i really liked the bell helmets because they have the adjustment thingy in the back so i can dial in my size. the shape of the bell helmets also seemed to fit my head better.

i'd try diff manufacturers. not sure how many you tried.

if you can find one that's somewhat close they also sell those foam strips to help size helmets .. but really i don't know if that's safe with bike helmets.

best of luck