Here is one I bought when I needed a sleeve for a Touch Lux 3 that I bought for someone else as a gift. Touch HD should have similarly fitting dimensions. With Touch Lux 3, there was even room for the charging cable in the sleeve.
It is not a soft sleeve, but quite solid. And it has somewhat of a stand function. And it was at $10 when I bought it
https://www.amazon.com/Dicota-Americ.../dp/B005F2TAI6
Does not seem to be available anymore at the supplier's website.