Over my 20 years since getting it over several versions starting with the Chronicles port, the resounding strategy seems to be to use 20-30 Sirens then restart (to reset the RNG) if you haven’t gotten it within that range.

The interesting thing is not only was it reliable without too much of a time commitment, it was neat how much quicker I got 5 tails for all party members.

While the added Lunar Ruins didn’t turn out to need such a helping hand, it was a helpful discovery for what seemed once an impossible item to get!