my local pball store always has gun bags in their used bin. i think i've got x3 of them for less than $20.
also, the dye navigator (best gear bag on the planet, eclipsed by no other
) has three padded slots that work pretty well. only problem with them are the fact they don't protect feednecks, so i hear my feednecks bumping each other, which prompted my to buy the gun cases.