Adult size bike trailer

I am looking for a bicycle trailer that will hold an adult of about 125 lbs. I want it for my friend with Down Syndrome, so that we can go for bike rides together. Ideally it would have a seat with head support, would be open to the air (not like the child trailers) and connect / disconnect easily to my commuter bike.

An additional feature that would be great (but is not necessary) would be if were somehow able to be used for carting around heavy loads like groceries, my softball equipment, etc.

Any suggestions? (other than getting a custom built one)

Can your friend pedal at all? It wouldn't work to haul your stuff around, but I seem to remember seeing an adaptive trail a bikeish thing made for larger kids/adults with poor head/trunk control. It had a headrest and a very secure seating arrangement, but allowed the person to pedal as well. I'll do a little research and see if I can find it.

*edit*
I'm getting closer - This doesn't have a head rest, but can come with a back rest and it requires some coodination and trunk control but I think searching for biking eqipment for people with cerbral palsy will lead me to the right thing, but check this out in any case.

http://caboosetrailerbike.com/

*edit again*
I've also found a trailer that can take a person up to 5'10 and 150 lbs as well this looks more like a child trailer, but I believe that the canopy can fold back so that the trailer can be open air as well as protected from the elements - definitely do a search for CP and bike trailers. I think you'll probably come up with many more ideas than these two.

http://www.wicycle.com/xspecial.htm