I haven't tried that, but it probably can't be done.
You could try... pick a frame on your timeline that shows your PF Source particle system the way you want to see it (as a potential object). Hide all other objects in your scene (or AltQ to isolate the particle system). Then do an EDIT/Snapshot, and use "mesh" as the output. Hopefully now you will have created a static mesh object of your particle system, and you can right click on the new object and change it to editable poly.
Not 100% sure it will work, but good luck.
Cheers,
Paul
Create a Mesher compound object, add the PF Source, then add an Edit Poly Modifer to the Mesher.