Sounds like a Sauer & Sohn model 1907 .32acp. The trademark will say 1905 but the gun is a model 1907. Magazines are rare but they are out there. Numrichs usually has some and you can find them on Gunbroker. You will have to search auction sites using both the model 1907 and model 1905 because many people don't know what they own. Let me know if you are having trouble and I will help you find one.
www.gunpartscorp.com is Numrich's website. Go to manufacturers under S. Select Sauer, select 1913. Then go to the last item on the last page. You will find magazines for $35 and change. They are in stock. Good luck and God Bless!