Brian,
It seems that a Ju88C of the Zerstörerstaffel/KG30 shot down a Walrus of 700 Squadron (on board HMS Suffolk) off Stavanger, Norway.
At least, if that's the geographical area you're looking for.....
One other problem. According following link, this was on 17.4.40:
http://www.wlb-stuttgart.de/seekrieg...r-verluste.htm
Another Ju88 vs. Walrus encounter or has someone a wrong date?
Regards,
Leendert