Okay! Just to wrap the whole thing up. I finally decided on a Aikikai hakama (from the local supplier). It's black - it's 35% cotton and 65% polyester - it's quite expensive - and it's the only option available within my short time frame.
By the way: it's a size 28 and it goes down to about 1 cm above the floor - that is when I push my hip forward the right way. It actually sweeps the floor when I don't, so I guess I'm in for a lot of falling during next weeks seminar - sigh
Perhaps I'll just talk my wife into hemming it up a wee bit
Thank you for all your answers !