Fish out of water here but thought this might be best place to ask for advice please. ds has to have a 3-season sleeping bag for D of E. Of our collection of , very underused, sleeping bags we have ruled out all but one which has lost its stuff sack and the label has frayed . How can we establish whether it is a 3- season bag or not ? Or can anyone recommend a suitable cheapish bag which rolls up small please . tia