Aerodynamic kid's trailer with suspension I'm looking for an aerodynamic kid's trailer to tow behind my Velomobiel Quest. Some corner points:


Needs to be attached at axle height
don't care for the coupling, because that needs to be replaced anyway
suspension is a must
large enough for one up to 8-10 year old kid with a bit of luggage, e.g. swimming pool stuff, something to eat/drink
two-wheeled (trikes can't tow inline trailers)
aerodynamics are pretty important
rain-proof


I live in Germany, so it should be sold here or at least there should be a vendor that ships here.

Edit: A bonus would be if there was a way to somehow carry a kid's bicycle on the trailer such that the kid can ride as far as he wants and then climb into the trailer and I can continue.
Generalisations on child-carrying trailers


Based on stroller designs, so suspension is rare.
Small wheels on cheaper designs.
Seat is positioned for visibility and for an adult not to stoop too far to attend to the child. This is bad for stability and aerodynamics.
Built like tents: frame with some kind of fabric over it. I've seen trailers/strollers with mesh fronts and ones with rollable plastic fronts, but as the overall shape remains a modified brick with fluttering fabric, I doubt they'll be very aerodynamic. Your velomobile is designed to have a minimised wake, so the trailer gains no aerodynamic advantage from following it.


What I would do: Make my own.


Find a suspended cargo trailer or design and construct one from tubular sections of aluminium or steel.
Create a fibreglass clamshell from scratch using insulation board for the former, like the Kingsbury Quattro
Or find a junk fibreglass boathull, invert it and add a vertical section until the interior height is sufficient. Fit a polycarb window on each side, but your child probably won't appreciate a porthole which shows the rear of your velomobile.
Use good hinges and hydraulic struts to hold the shell open (like a car hatchback)
If the shell needs catches or straps to hold it shut, there should be a release mechanism on the inside.