There is an original and two repros right now on Ebay. The original is up to $53.50 and the repros are both under $25.00. The repros tend to be crap. The originals can be fairly pricey but they aren't being made any longer so it's a seller's market.
Every aftermarket I have ever tried is crap. As a matter of fact, I have a Triple K (or Triple Krap) that I would not even GIVE AWAY to anyone. It really is that bad, and it was brand new. One of my early mistakes. /forums/images/graemlins/confused.gif
I have several 1903's and have even twice bought guns that I did not want (because I already had that variation in better condition) just because it had 2 or 3 NICE mags that I wanted and could not get without the gun - as long as it was priced right. Then I rotate in one of my lower end magazines I have and sell the gun.
I guess what I am trying to say is, nice ones are not cheap or easy to come by, but be patient. I have one original or at least correct vintage in each gun I have and 8 or 9 spares, and I have not put more than about $60 in the most expensive ones I have.