Non-Theme Beans widget buttons display improperly on iPad

I'm experiencing this issue with non-Theme Beans widgets in the Blooog sidebar:

In Mac Safari the widget (a subscribe field & button) displays properly, inheriting the button style from the Bloog theme. However, In iPad Safari, the Theme Beans Twitter widget button is correctly styled, but the subscribe widget button uses an ugly stock button.

This has happened with multiple widgets, so it doesn't appear to be widget-specific.

How can I force the subscribe widget to use the Bloog theme button style?

Thanks!