It depends on the brand. I have a commercial acount with Red Neck Trailer Sales and you can order different brake drums for several manufacturer's axles.
Are the brake backing plates welded to the axle or are they bolted to a brake flange on the axle? This will be a good determining factor. If they are welded your screwed, bolted you stand a good chance. You will also need to know the bearing numbers out of the hub and drum to identify the spindle.
for the extra money involved just get 2 braking axles.
When I was looking at axles in trying to decid how to get my junk to the trail it was looking like $250 ish for the tube. That was torsion 3500 lb axle, spindle to spindle, no brake parts/hub.
Just because it's welded doesn't mean you can't get a standard bolt pattern brake drum. See if you can determine the brand then go on www.redneck-trailer.com to see if they offer a drum.
Check your state's laws. In Colorado you have to have brakes on any trailer designed to haul over 3000 lbs and both axles have to have brakes.
A welded backing plate tells me that the axle is a 2800# cap axle, they were only made with the mobile home bolt pattern, there is not anything that can be used in it's place. Sorry for the bad news, but you would probably be better off buying new stuff and not worrying about it. If you were closer I could make you a good deal on a set, but freight from California will kill you.