Does seem pretty poor. I guess that's why they're going cheap
Mine has just turned up and it is only the keg. No tool wrap or internal cap inside the lid. I'd be very disappointed if I'd paid 12 quid for this!
They usually have a sleeve inside to stop rattling against the plastic and the opening is far wider than a water bottle so makes it easier to take stuff out.
Seems to me you could just use a standard water bottle. Can't see anything in the description that suggests it includes anything special to stop your stuff rattling around.
On one of the may other bottle cages that you can fit to your bike. If you see some ridiculous touring bikes, you can even fit them on either side of the forks for a joke!