I've got one stem bag for sale if anyone would like it give me a shout.
Made by me.
This one has a denim outside pocket.
Drawcord top closure
White Rip-stop internal floating liner
Webbing loops for attaching stuff (or moving the strap position to suit your bike)
Comes with velcro straps and an adjustable elastic cord for attaching to your bike.
£20.00 inc UK postage (a bit more for international shipping)
They fit like this. There's two velcro straps supplied, one to attach to your stem, one for your bars. Plus an adjustable elastic cord at the bottom to go round your headtube.
I'm no pro but I've been using one on my commuter for a couple of months and it's held up great.
Check this other thread were I sold some to see happy customer feedback :)