Looks like some of the features I was looking at in 7.9.2 are also in 7.8.1
Perhaps, You could try this.
Go To Alert and Actions and create a Metric Threshold alert this is the more General version of the Inventory Alert.
Then you could try Create Alert Per and put your Instance field in that. It will need to be a Keyword Type
That should generate alerts by Instance and then that instance should be part of the alert context.