In reply to dek:
I guess it depends a lot on if they are going to use it again. No point in spending loads on something that will get used once then live in a cupboard. Maybe army surplus type place would be a plan if only going to be used once?
CMM and Decathlon if you have one near are always a good shout too.
Something comfy is probably the main criteria. Way back when our group used a mixture of old external frame rucsacs and things like Vango Eastwinds and our shoulders ached(and we moaned) the whole way.
I'm probably just stating the obvious here though!