Haha, now I see why the "newbie" right below my username is coloured bright red. Checking this with the forum was definitely a good choice.

As for the post, the diameter is 27.2 mm. Length from the end of the tube until the min. insertion point is ~180 mm.

I'll check a LBS first thing tomorrow. Hoping to get one around 350 mm for not much more than 30€. I guess I'll just have to see from there, none of the stores really properly display all of their products, just the bikes at best.