For round barrel fowlers I make my own lugs out of thinner sheet metal, usually brass. You ben it over to form a T, then file it even thinner and then put the bend in it. Sometimes making this stuff is easier than using the bought stuff. I have soldered thm on with 50/50 solder with excellent results adn use a silver solder with a higher melting point to form the lug but have also just used the regular solder as it resets.
DP