At one point, Finfolk was top on my list for a custom tail. At one time, they were super speedy with their work. Unfortunately, even though I'm pretty sure they or Merbellas would make the most magnificent creation, I wouldn't stand the year plus wait.
Honestly, I'm sort of dreading when the current mermaid craze bubble bursts and all these tailmakers start losing business when mermaids are no longer the current in thing.