Joss Whedon has two of three pairs of goggles. NPH has the third. The "hero" set is in Joss' possession. (The other two don't have flip fronts)
In MANY, MANY months of searching, those are the only props I have definitively tracked down. The labcoats seem to be put away in storage, but that can't be confirmed. At least 3 were used, based on the number that have shown up at cons, events, and can directly trace their lineage to the show. The first is the standard ivory color, the second is ivory with a hole in the back to ratchet Dr. Horrible back after Captain Hammer hits him, the third has been dyed red. (And was used as a standard ivory one before hand)
The labcoat and stun/death ray were both used on Firefly, and the labcoat used for Aliens before that. So, there does exist a possibility that you could track down one used on another project...But that sort of defeats the purpose of "Screen Used Dr. Horrible" stuff, since it wasn't actually used on the show.
I'm holding out hop that a few things can be found.
-Nick