[GMCPaul]

Here's what we know on the subject...
We've checked as have most other suppliers of these and haven't found any sources that have any left in stock. The original manufacturer had their factory closed over emission's reasons and that manufacturer has yet to locate a new factory to make them in yet and doesn't anticipate having them available for at least 5-6 months.
BUT a different manufacturer supplier of spindles here in the USA located the last pair and they have already provided them to their factory and are currently in progress of making them. But this takes time for new molds to be made, first castings completed, quality check of them, then approval to manufacture, followed by CNC machining & spindle pins. Anticipated to available in May 2019 hopefully if things go right and they do have a priority on them.
So you'll with a 99% certainty need to find a set someone's previously purchased that is willing to part with them.
Currently it is only the 3/4 ton disc brake drop spindles affected as the stock height 3/4ton disc brake spindles are in good supply.
Paul Jr @ GMCPauls