USD prototypeRoot Primvar change in GN?

Hi,

I’m trying to export a simple GN setup from Blender but I’m having an issue with the prototypeRoot primvar externally. I want to be able to set the primvar to the name of my object (or vice versa) when exporting from Blender so the USD point cloud knows which instance object to put on which point.

This is all I have done so far. Just a couple extruded cubes in a collection that I want to have instance correctly externally.

If anyone has achieved this is would be great to know what you did!

Thanks