I have got a Lowepro DroneGuard BP250
There is enough room for my Mavic 2 Pro with smart controller extra batteries and a Lumix camera.
Also got room for a 10" tablet and a 15" laptop and room to carry some food.
Longest ride so far has been 60 miles and it was comfortable.
Bought a waterproof cover for when i get caught out in the rain.
https://www.amazon.co.uk/Lowepro-LP37099-DroneGuard-BP-250/dp/B06XGMZL8W