A follow-up to say that I took the plunge and bought a couple of these batteries. They charged using the Bose QC3 charger and I tried them out on a recent TATL.
No complaints so far - The battery has survived over 10 hours of use so far and is still going strong. Some of the reviews mentioned that some of these alternative batteries are not an exact colour matche with the QC3, but I can't see any major difference with mine.