Tri-state checkboxes

[Mark Powell]

I know there is debate among HIF designers that such a thing should
exist in the first place, but let's assume that one has a good reason
for it:  

My question is, is there any Rev-native way of doing tri-state
checkboxes?  Where a checkbox can have an ON, OFF, or "equivocal"
setting that signifies something between ON and OFF.  If not Rev-native,
has anyone cooked up their own solution whose look and feel is
cross-platform compatible (so that the tri-state checkbox can be ganged
alongside conventional Rev-native checkboxes, and not stand out like a
sore thumb)?

I am on 2.8.0

Mark