There is no parent binding access in lists or any other mvx data binding context currently.
There are plenty of simple workarounds - see questions such as MvvmCross Android - Alternative to RelativeSource binding for button command for some suggestions.
I've answered questions similar to this several times. Each time i invite people to raise feature requests, ideas or pulls to issues such as https://github.com/slodge/MvvmCross/issues/35 . While there have been perhaps 3 or 4 of these questions, no-one ever seems bothered enough to follow up, so i guess it's not an important feature.
