If you’ve been looking for Post Grape Nuts and can’t find them, we understand.
There is indeed a shortage. Of course, rumors are flying as to why, so the company shared "We would like to inform you it has NOT been discontinued. We are currently experiencing a product shortage where we are not able to fill orders for this item due to adjustments in our production schedules and production availability."
The product should be back sometime next month.
Source: Good Morning America