There's a long thread about covers for the Sony T1 here:
https://www.mobileread.com/forums/sho...d.php?t=152798
Most of the suppliers seem to supply covers for the Kobo as well.
I've been happy with the Navitech cover I bought for my T1, and when I bought a Kobo WiFi as a present a few weeks ago, I also bought a Navitech cover for that
http://www.navi-tech.co.uk/garmin-nu...bo-accessories. They were very similar, although I thought the Kobo one was actually slightly better quality. The pics on the Navitech sites aren't great; most of the ones for the Kobo look like the one I bought for the T1. The one I bought for the Kobo was the one they call 'red bycast', but it was a much brighter (and IMO, nicer) red than it looks on the website; the pic on the website looks almost brown.