1 from Event rewards, 1 from RNG Tickets during the Event (many people farmed Tiamat like mad for an extra copy), 1 copy from Eidolon Orb Store
let me correct this a bit - 1 from Event, 1 from tix saved in *income* box, 1 from EO shop

the reason - Tia stats are as terrific as her Boobs size