It doesn’t seem like Yamaha makes separate cases besides replacements for the P-32D pink and blue models.
Here the P-32D (blue) with a new soft case:
Here’s a link to a search on Rakuten (Japan):
There seems to be a lot of soft cases & bags available, most of which aren’t made by Yamaha (or other makers). I have noticed a trend, however– this last year makers have been releasing a soft case option for their instruments. So maybe we’ll see some variety soon.