Cape gun sight

[LAGS]

You can use a larger drill bit , nail or brass rod.
You can always file it back down to the height you need.

[Cap'n Morgan]

If your front sight looks anything the the one my gun, the easiest fix would probably be to file down the old sight post, file a lengthwise slot in the remaining base and soft solder or braze a new blade in place - brass would do fine. Make the blade a bit too high to allow for a final adjustment and add a nice sloped/rounded profile to it.
My gun has V-notches in the rear sight blades, meant for keeping the "ball" in the front sight matching the "V" but I much prefer a flattop front post for height alignment.

[Wayne Smith]

I do have some brads, which would be easier to adjust with a file than a hardened drill bit. But the drill bit is just around the corner at the local hardware store.

[DougGuy]

Arghh.. You'd likely be adjusting a drill bit with a dremel tool, may be too hard for a file. You could use pieces of guitar strings, there you would get many different diamters, .052" is a popular size, .046" is a popular size I would seek out a guitar or instrument repair shop and see what you can find. If you superglue the windings of the string will be a good grip for the glue or you could also use some of the 5min epoxy from lowe's to hold the string in place. this would give you enough shots to see if you need to go bigger or smaller with the string, this is to give you an accurate idea of how much height correction you need, then you could set about a proper repair in steel. They also make stainless steel strings.

If you can't find anything useful without a lot of trouble, I probably can scrounge up a few short pieces of nickel wound string.