Thank goodness my wife just found mine behind the couch. I finally got Sonosax to respond to my inquiry about a replacement. If you need an extra you might want to read below and grab the final tray for a mere $82USD.
In the meantime, I ordered the brown ones from Newmark linked above and will report back if they work.
Dear Mr Kreider,
This is just to confirm that there is only one battery tray available, our last one.
The total amount of your order is :
CHF 30.- battery tray
CHF 50.- shipping cost, via UPS
CHF 80.-
An advanced payment would be required and could be made via Paypal to sonosax@sonosax.ch, if it is OK for you.
Best regards.
Gloriane Moulin
SONOSAX SAS SA
CH-Le Mont-sur-Lausanne