I would imagine that ration bars would be something you'd only get from guilders (since they are also the only source of guardsman grade fighting gear.) But they'd also be more expensive.
If you can adjust a probablity thing on the lost supplies thing, I would imagine ammo and PDF/Ganger weapons would be the most common, followed by lower end melee weapons, maybe an inferior or heavily worn out version of flak armor that uses carbide as it's material or whatever the one for scrap body armor is, and the rarest possible finds being power weapons or even an occasional bolter/bolt pistol (Ammo would be obscenly expensive, since, while not uncommon, bolters are a bitch to take care of and get a hold of if you aren't a space marine.) If possible to tag a syndrom to a bolter round, then I would imagine that would be something akin "loss of limb" that would casue the affected part to explode/boil. Pitty the poor hiver or outlaw hit in the body by one. (Again, if possible to manipulate probablity, these would be so low you'd need to be blessed by Armok, the Emperor, and the two gods of all dickery, the deciever and Tzeentch, would have to be in a good mood.)
That'd mean any discoveries of lost supplies would make players do whatever it takes to get a legendary miner so they can have thier dreams crushed when all the find are two boxes of autogun magazines, a crate of ration bars, and a carbide riotshield.
And the cries of dispair would be great. Although alot of others would consider it a miracle if they got such items as it stands.