Chicken its pretty easy to cut a dovetail in the barrel. Then you can use any sight you want.
I use the vented nipples in mine. I use to buy them from Mountain State muzzleloading but they are out of bussiness now. They were called RedHot, Firehot or something like that. Don't worry. somebody will along to give the correct name.
Also if you are having misfires check this. Take out the clean out screw by the nipple. Shine a light down the bore and make sure the hole is drilled all the way through to the barrel. I had one gun that gave misfires and when I checked the hole I found it wasn't drilled but partway through. I ran a proper sized drill in the hole and the last little bit of metal crunched out and the gun fired sure after that. Just a thought.