You should email your affiliated organization to see if they are able to provide this. Here is an example you can copy:
Subject: Certificate of Liability Insurance Needed
Hello,
We require a Certificate of Liability Insurance to participate in our Downtown SLO Farmers' Market. Please reply with a Certificate of Liability Insurance attached with General Liability Coverage of $1,000,000.00 per occurrence and $2,000,000.00 aggregate. Here is an sample: Certificate of Liability Insurance Sample
Thank you