Hi bote, since no one has commented I'll take a stab at helping you.
1. If you haven't already done so I would suggest educating yourself about Krag bayonets. The following sites are good places to start:
(You need to Login to view media files and links) (You need to Login to view media files and links)2. How much are willing to spend? Simple enough... you want the good stuff than your going to pay the big bucks most of the time. Not saying that good deals aren't out there.
3. The usual places like Ebay and Gun Broker are good places to see what's available. Also, other online sites like KCA might provide opportunities to purchase Krag bayonets. Just type "Krag bayonet" in your favorite search engine and all kinds of stuff will pop-up.
4. More specific stuff would be:
a. Most of the time look for two rivets that attach the walnut handle grips to the tang not screws.
b. Look for a pommel shaped like a birds head.
c. Most blades had a grove or fuller on both sides.
d. The part of the blade near the hand guard or ricasso will have the date of manufacture on one side and a US on the other.
5. These are just a few things to look for