Thanks for your offer to make pictures, but it won't help me. The issue is that you have to be able to reach for the reservoir while (slowly) driving the last metres to your home. The location under the passengerseat looks good, but I wonder if I can safely pull the handle.

I do know the Scott. Same purpose, but a different solution. The Osco is not automatic (you've to pull the handle yourself) and is not connected to anything of your bike. It's really a simple solution and therefore I have choosen this one.