1) craft (leatherworking): making a bandolier modified to potion size should be relatively easy.
2) the 3.5 magic item compendium had a weapon property called "metalline" which did this for the weapon (allowed change from cold iron, silver, and adamantine), but i don't know if something similar exists in pathfinder.
Price 5 sp; Weight —This leather belt is worn over one shoulder and runs diagonally across the chest and back. It has small loops or pouches for holding eight objects the size of a flask or small dagger. You can use the "retrieve a stored item" action to take an item from a bandolier. You can wear up to two bandoliers at the same time (any more than this and they get in each other's way and restrict your movement).
Dedicate it to potions in flasks, and you are good to go for #1.
There are Weapon Blanches for adamantine, cold iron, ghost salt, and silver. They are best used on ammo, since they don't last long.
/cevah
There's a often-missed rule in Pathfinder that a weapon with a high raw enhancement bonus (A +5 weapon, but not a +1 keen holy weapon) gains the ability to bypass various DRs, based on just how high the +X is. For this reason, you can just invest in a strong +X Amulet of Mighty Fists, which you'd likely want on a natural weapon/unarmed attack character in the first place, and eventually gain the ability to bypass most of the common DRs you'll be facing. However, as, unlike normal magic weapons, the AoMF caps out at a +5 total bonus, you won't be able to take special properties on it (keen, etc) without sacrificing some of your DR coverage.