You MUST be in The Immortal Flame's to obtain the leg piece. I've always loved this leg piece but it didn't feel... idk, open enough? XD Feel free to mod it to your liking \o/
[EDIT] A note from SifridExtan "[Small note: You not only need to be with the Immortal Flames to obtain the piece, but also to glamour/equip it. If you change to a different GC, you won't be able to equip/glamour it anymore]"
Thank you for the reminder!