I bought something (possibly West Marine) a few years ago, green color, and was safe and effective on fabric, but I forgot what it was called. There are a few commercial products out that claim to work; BioZap and MoldStat are two of them. You can try this homemade remedy (not mine... I found it on the web), and see if it works for you:
"Some people are allergic to bleach or the fumes make them sick. This formula does the job without the reaction to bleach:
Non-bleach mildew remover:
1 cup white vinegar
1 cup Borax powder (available at any grocery store etc.)
2 cups warm water
Mix ingredients in a bucket or in a spray bottle. Apply to the mildew spot and leave it on for 10 minutes. Rinse afterwards."