Based on this product's specifications, here are some alternatives and similar models
Mobile phone battery Sony BST-39 — Li-Pol 920 mAh, compatible with Sony T707, W380a/W380c/W380i, W508, W910i, Z555a/Z555i
Summary description:
Rechargeable Li-Pol mobile phone battery Sony BST-39 with 920 mAh capacity. Designed as a replacement for Sony models T707, W380a/W380c/W380i, W508, W910i, Z555a/Z555i. Restores device runtime and standby time, suitable as a spare or replacement for daily use, travel or extended calls, and fits the listed models.