Using Tags to filter portfolio items

Hi there,
I am hoping to use the portfolio option to display a group of speakers for a range of events.

They speak to a range of common topics and I have used categories successfully to allow the user to filter them.

My challenge is that I have a range of events and quite often the same speakers present at each, but not at all and then we often add in local speakers. So my thought was that I would use tags to filter which speakers are attending each event. But I cannot find any option to select the tags in the grid portfolio component. I can not use categories for this task as they are already used for topics.

I am using the Ajax Component, which is excellent.