FYI I think the alpha chumbys are covered with synthetic microsuede type fabric. The speakers and bend sensor are held in place by cotton voile. The difficulty is that the less firm the fabric, the less sleek the design of the chumby. You get some stretching and bumps in the seaming. The new chumby looks a lot more professional and attractive from the design perspective due to the firmness of the leather. The durability of the fabric is also key. Leather is able to be cleaned and wears well, so I think it is a sensible and well-considered choice.
I've managed to create nice-looking outers using wool felt and cotton fabrics that have been adhered to acrylic felt, to give you some alternate possibilities if you'd like to craft your own cases. But then I might get arguments against the mulesing of sheep, the toxic chemicals used on cotton crops, the petrochemicals used to create synthetics & plastic parts...where do you draw the line?
I'm just impressed that bunnie has spent so much time in the factories, making sure that they choose one with adult humans that are treated fairly and documented this process. It is far more than a lot of companies do.
Organic fabric options might be nice and do-able (although costly) for third-party "makers". However, I have only seen organic fabrics in lightweight woven and stretch. Do you have any suggestions for heavier weight organic fabrics? Sources?