Had the Part, and Got It to Me!
After searching long and hard online, I found DAP, who looked like they might have what I needed. Most everywhere else said they'd take the order, but didn't have the 'nationally backordered' part.
I talked to a rep at DAP, who said he was pretty sure he had one of the item in the warehouse, and that he'd go check and call me back. He put his hand on it, and called me. I placed the order immediately, and I had the part in hand in three days.
Great service!