Transfer the heirloom marked weapon (with the rune) to the correct character, unadorn and put the notrade rune on the weapon you like. But it's easier (and cheaper) to get the flag for the follower blue rune https://u.eq2wire.com/item/index/700397161 on the live servers Having the flag you can buy the rune in Myrist
Trader Frank in the Hypogeum (Entrance to Fabled Drakkel is in Myrist) sells the Ragebourne Insight and the Vindicator's Rune of Greater Myteries once you have the flag. Both are Heirloom