Amazon has the VF-11 external optical viewfinder for the Sigma DP1 in stock at a price of $87.61 with free shipping. That's nearly 40% cheaper than other reputable dealers like B&H ($150 plus shipping) or Adorama ($140 plus shipping).

I just ordered mine. You can help support this site by using the link below to purchase yours.

Update: I received my VF-11 viewfinder yesterday. Like the CV minifinder, this is nice and small, appropriately so for the DP1. Having heard the knocks on VF-11 (plastic build, marked barrel distortion, difficult to view brightlines, and lack of parallax correction), I have been pleasantly suprised. The build seems very solid, and the view is large and bright. I can simultaneously make out all brightlines while wearing my glasses, which is something I had more difficulty with using the CV minifinder. Barrel distortion is moderate and I don't anticipate it being a problem for my intended use of the viewfinder. The VF-11 seats snugly in the DP1 hot shoe; I don't think it will dislodge easily by accident. I had been waiting for a good deal on the VF-11, and I can certainly recommend it at this price.