An omnibus of the fourth, fifth and sixth titles in this series (including one that was a Historical Dagger and Barry award winner) is on sale at Kindle UK for £3.99. I don’t see a similar omnibus even available in the US – if someone finds it, please add info in the comments!
Titles included in Berlin Noir 2: Further Adventures of Bernie Gunter include: The One from the Other, A Quiet Flame, and If the Dead Rise Not.
Buy: Kindle UK
Note that the previous omnibus, with the first three titles, is still on sale for $1.99 in the US, although sadly not still on sale in the UK. Info and links are in this previous post.