So far I haven't seen a silicon case. Actually I think the leather case makes good sense b/c E-ink screens are more fragile than usual LCDs. The brown case sold in Amazon, Passion of Book, appears better than the standard case (black).
PS: I also purchase through Amazon. I already contacted
sales@onyxboox.com regarding updates and warranty. A representative called Gera kindly responded to my email with the firmware link you posted, which, unfortunately, does not work on my M92.
Anyway, I do hope Arta Tech guys, either in US or in Poland, can catch up with other distributor like booxtor in developing. Actually, I do not quite understand why the extra work on TTS and cloud service takes more than two months (so far).