The recent Runaways find was me, I got a total of 5 copies in a small random collection I bought earlier in the year. Sold three copies at ARC, and one privately.
Shellacshack has been periodically listing copies since 2003-4. He must have found stock somewhere back in the day, but he won't reply to inquiries on how many copies he has left or when he will sell another. Truth be told, his 45 auctions don't always seem to garner a whole of fan fare, which is often good for the buyer. He is a well known 78 dealer who helped write a 78 price guide.
If you look at old popsike/frenzy listings, you'll see his tell tale listing style in the description of several of the results, where he grades 45's according to the 78 grading scale.
The Trackers was also me, I had originally purchased only 10 copies, but over the course of a couple years ended up with around 50+ copies before they were all purchased from the source. A large chunk of my copies went to Wickham, who has been responsibly leaking them out to protect a reasonable price for both the seller and buyer.
Post script! Just now looking at the auction that was linked... This was a totally different auction than what I was referring to earlier. I hadn't even seen this listing up and I am always searching garage 45 auctions on ebay! It must have been listed around the same time the Shellacshack listing was up. Wow, I have no idea where this other copy came from, but I seriously doubt it came from the copies I found.