ebay.
The seller said it was grown by Frank Kroeker, and it was shipped from Nebraska. So, when I googled Frank, it brought me to this forum. Frank goes by T-Town Bonsai here. He used to work at Brussel's, and has (had?) his own bonsai nursery. Since I've been reading the threads here, I have seen several examples of his rough stock turned into some really nice bonsai.
Back in the day when I was first starting bonsai, stock like this just wasn't available. At least not here in the USA. I used to subscribe (via Bill Valavanis) to "Contemporary Bonsai", a Japanese language bonsai magazine that had advertizements of stock like this for sale. But at that time, no one here was. At least, I didn't know of any.
But today, with the Internet, it is possible to find information/people/resources that were impossible to find in the old days.
Back to this tree... I've been watching ebay for a while. And this is the best pine stock I've seen in a long time. Brussel's has some "finished" pines there, with big prices. I can't afford those. George Muranaka has some decent stock for sale on ebay, but he doesn't grow using sacrafice branches. My other thread on JBP shows one of his.
My plan for this stump is to do some wiring to open it up, and fertilize heavily for new growth next spring.