I got something similar to this in 2007 from Costco.
http://www.amazon.co.uk/gp/product/i...49011&s=sports
Has got lockable zips and covered over back straps. No detachable secondary bag. Not sure about the capacity but it's a big un, kind of semi rigid with a bit of a GRP/Carbon Fibre frame. Grap handles and a pair of carrying handles. It's very tough and has served me well. Long way below your price indication - I saw similar in Costco a month or so back c £35
