You don't need to weld one up, get a piece of 1" all thread 1 foot long a piece of 1" pipe 10" long a couple 1" washers and a 1" nut. All this can be had for about $15.00.
Drill a 13/32 hole in the end of the all thead and tap it with a 12 X 1.25mm tap. Screw the 1" all thread on the spindle pin, slide the 1" pipe over the all thread followed by the two 1" washers and the 1" nut. Be sure to grease the all thread and the washers.
This will work just fine if you are only doing one Z. The loaner program will also get one to you, the cost will be about $22 because of the postage rate increase.
I also sell one on eBay for $114.99 that is welded and has a thrust bearing and a 12X 1.25mm helicoil in the end.