The A400 is a fun little mini, but I along with others have had issues with accidentally pressing one of the buttons on the ring. To correct this I have created these two models.
One has cutouts to make it easier to access the buttons if you want.
The other one doesn't, but the plastic is thin enough that you can still press them if you want.
They are a pretty good fit, but if you are an aggressive player you may need to use some thin two sided tape.

I share my designs for free.

These should not be sold, if you want to sell them then contact me to discuss.

You can print them for friends, family, etc but don't charge more that the material to print them.