I've had a few people over the past couple years now complain that there never seems to be any "little" or "skinny" pens available from custom makers. I admit it does seem to be a little more difficult to make this sort of thing. The clearances have to be tighter and the parts are definitely more fragile. I decided I would make a couple pens to suit this crowd. Both of my new ones are from Conway Stewart blanks which I am learning to love more and more each day. They polish up beautifully and make great pens. Both pens are gonna be around 5 1/2" in length capped and right at 5" uncapped. Both have 11mm to 10.5mm sections and both will feature #6 Jowo nibs. This section size is about as small as I can get a section with a #6 feed and housing.
On the special order side of life I am currently at about 2 weeks give or take. I have a couple of orders going where I am waiting on materials to arrive. If you have something in mind send me an email and be sure to put "pen inquiry" in the subject line so I know not to "junk" it. I should be able to get to your idea pretty quickly.