You can try
Powder Horns & More
I have never ordered from them, but I know they have been around for a long time. They show pictures of individual horns they have for sale, so you pick the exact one you want, which is great. Their prices are very fair. Most dealers who sell horns just sell "pot luck."
I disagree with the Powder Horns & More guy regarding the choice of left or right side carry, though. For me, a horn from the right side of the animal's head carries best on my (preferred) right side. The curve of the horn fits my side, and the tip points up. He recommends using a horn from the
left side of the animal's head to carry on your right side. This means you have to rotate the horn toward your body so the curve fits, and the tip ends up nearly horizontal. That's the way a lot of people seem to like them now, though, and I think individual preference has always played a part. An artisan and horner named Mark Elliott adressed this very eloquently. You can go to his website (
right here) and scroll down to where it says "Left or Right Hand Carry?" In any event, you can look at the actual horns on the Powder Horns & More website and make your own choice. I don't know of anybody else who offers that.
October Country sells raw polished horns. I don't think you can pick the actual horn, but they do offer a choice of right or left hip carry. You specify when you order. I bought one of their finished "Frontier Horns" a few years ago, and it appears their assessment of right or left side carry is congruent with mine, or at least it was at that time. I would like to add that the horn I bought from October Country is very well made, and authentically styled. I think October Country's Frontier and Yellowstone model powder horns are a "best buy" on today's market, if you want to get one readymade. Both are very authentic, and fairly priced for what you get.
Good luck!
Notchy Bob