This is a paid asset, but now you can download 2D Buttons Free.
Detail this asset from Unity Store: Original Link
2D Buttons v1.02.20.4a (Latest version)
“If possible, please buy the package to support the developer”
This package contains a huge variety of 2D buttons. PNG files have 2048×2048 pixels and 256×256 pixels each button.
Several example scenes included.
It contains transparent icons.
Bonus: Icons + Fonts…
All buttons ready to be used in your project.
More??? Visit: Composer UI
If you like this pack – feel free to rate it. 🙂
SWG2 – Visual Solutions