Hello,
I'm a Filemaker developer over 6 years and system administrator over 18 years. I can quickly install an SSL certificate on your server. But I need more information about your server: what of Filemaker Server do you use (old versions of Filemaker server don't support every certificates, only from some publishers)? What certificate do you have?
I will glad to discuss your needs and help you solve your problem.
Best regards, Andrew.