I’d have a look at the North Face duffle bag thing. I’ve got the 90l one and its ace. Use it for weekends away, races (fits shoes, helmet plus all my kit), straps are comfy and it can be worn like a ruc-sack if you’re also pushing a bike bag. Think they have a pretty good warrenty on them too, as in – it breaks, you take it back to the NF shop and get a new one.
This is the 140 litre one, I got the 90l one during their 10% off sale, which was nice.
140 biggun
Failing that, Troy lee do one with a fold out mat thing for changing your shoes. Its nice, but its pretty expensive and not as robust as the NF one