Like Trevtassie I use a Frio evaporative bag. All it needs is water and keeps meds cool in even pretty high heat situations.
I've survived months with just a frio bag and no refridgeration for my insulin. Though can't remember exactly how large an amount I was carrying. I always bought a penfill pack for both levemir and novorapid so five penfills of each. One penfill of 300 units would last me around ten days or less so I'd use them in two months or less.
My insulin survived significant amounts of time in 30+ degrees celsius outside shade temps (a few weeks).
I try to keep the frio bag in a shady protected area on my bike so usually under my rack bag. Can't keep them in a pannier since the evaporation won't work if stored in a place where moisture can accumulate.