secure multisite

I'm setting up a multisite setup (using separate databases for the sites, on the same server) and can't figure out the security problem. I need login pages, forms, etc, to be secure, which normally I'd use Secure Pages for.

Problem is installing a site certificate that'll handle the different domains. It seems clear that SSL can only apply to one domain per IP address. As I understand it, TLS Extensions seem to take care of this problem, but is not supported in many common browsers so I can't go that route.