If you are searching for one, ebay is your best bet as they are fairly plentiful. I accidentally found an item listed under "jabra wave" that appears to be a different product, but uses the exact same shell as the BT250v. There are a couple selling for under 20 bucks right now.
This picture was posted on the RPF shortly after I announced my find of the earpiece used in a Jack Harkness ear piece.
Based on the success I had in my previous hunt, I decided the same methodology was in order. This basically meant using Google image search in combination with Amazon.
The key points I was riffing off from the picture are the three slices in the ear piece along the top of Jack's ear, and the near vertical line on the part under his ear lobe, where it transitions from the ear piece into the mic with the word "Torchwood" on it. Also, I made the assumption that this mouth piece was an add on. You can also see in the picture what appears to be a button on the piece under his ear lob.
A few pages down, I found this image, which looks like it might be the right ear piece, but obviously this was of the opposite side of the thing, and has some minor differences. But I was definitely on the right track.
I zoomed in on the logo and realized it said "Jabra" which helped immensely in my search. Then I just looked for "Jabra blue tooth" on google, and was very quickly led to this picture, which I think is the right one.
This picture comes from this website.
It's not that good of a picture, so it's hard to see details clearly, but all of the tell tale signs are there. The color cannot be confirmed, but it looks pretty darn close.
I've found that there are some non trivial differences between the Jabra BT250 and the BT250v, the main one being the color. I'll need to go and watch the episode that this one appears in to be sure, but I'm feeling very confident that it's one of the two Jabra sets identified here. There's also a BT200 that has the same body shape, and the coloring is different.
I actually like the BT200 the best, but the upper ear piece is not black. Definitely need to go watch that episode.