If Arizona Hobbies website shows a color out-of-stock, you can backorder it and it should ship within a week.
Because the bottles are plastic, some solvent may have escaped through osmosis. Fill the bottle with thinner to just below the neck and that should be the correct amount of solvent to pigment. Of course experiment to see what works best for you.
Tru-Color Thinner works for both Air Brush Ready and Paint Brush Ready formulas.
Arizona Hobbies website will not allow the choice of Media Mail for orders that include non-Media items such as paint. Media Mail is only for books, videos, maps and other printed matter. Priority or First Class mail must be used if ordering non-Media and Media items together. The paint bottles don't weigh much and often if paint is purchased on a separate order from Media, total shipping costs can be reduced.