File out a slip over sight from metal and attach it with low temp silver solder.
Heck, you could even use black colored Acetal (Delrin) plastic and glue it on.
It's available from Enco (
www.use-enco.com)
You could also use aluminum and a Dremel tool to open up a slot from just the one side. Shape it and use aluminum black on it. You would have to be careful with the Dremel in making the slot, but it would allow a sold front to the sight.
Now you have a few other ideas. Pick from mine or one of the others suggested and go for it...Have fun.
It might take a little work, but if it's just temp until you get another barrel, it might be the best option. The try sight that was mentioned in an earlier post is a very good idea. Then you will know how high you need to build the sight. Leave a little extra for fine tuning on the top.
A piece of metal with a slot filed through the middle, but not all the way to the top would work. You can then thin out the sight at the top for proper width.
Kind of a Bubba fix, but it might be the easiest way to do the job.
Best Regards, John K