As was stated the half case is actually the bottom half of the factory soft case.
The Super Program soft case is actually fairly common and easier to find as cases go especially since it was a newer and widely produced camera body.
You can actually stuff an MX into one (a much harder camera to find the soft case for) and still have it hook correctly over the strap lugs though an MX is the tiniest bit too large for it.
Here is an example though this one costs as much as the damn camera does on there (like new though):
Pentax Superprogram Case and Strap | eBay
If you don't mind age cracked vinyl on the top half they are available cheaply used depending on shipping. They tend to age somewhat poorly so finding older ones in decent shape is more of a challenge than newer ones.