How to transfer ringtones from iPad to iPhone

Hi there, I just purchased a ringtone from iTunes, using my iPad.

I can see under Settings- General- Sounds- Ringtones. However, I can't seem to find it when I open the iTunes on my iPad.

There is no 'Tones' section, it's also not under the 'Purchased' section.

When I buy music from iTunes using the iPad, it's all automatically sync-ed to my iPhone, why it's not the same with ringtones?

I would like to transfer this ringtone to my iPhone, but no idea how to do it.

Can anyone please help? thanks very much!