Hi Nick,
It looks like Native Mobile Resources includes bar chart (beta) – have you had a look at this?
Source:
https://docs.mendix.com/appstore/modules/native-mobile-resources#2-native-widgets
https://github.com/mendix/widgets-resources/tree/master/packages/pluggableWidgets/bar-chart-native
This post has some info on it – 5 months ago it was in beta
https://forum.mendix.com/link/questions/95723