Depending on the op-amp and gain, it might be a bad idea to use a leather case anyway, unless someone decides to make a leather case with a fully open back. The device can get pretty hot.
Also for new buyers, don’t forget to install the 3m rubber feet (comes in the box) underneath to allow some airflow and a bit cooler operation.
How about this one? There are punched holes on the bottom.
If it's not enough, I think you can ask them to make a customized version with fully open bottom.