i using multisite with domain mapping. all my sites mapped

HI,
i using multisite with domain mapping.
all my sites mapped to domain like: http://www.domain.com
now some of my clients ask me to add ssl to their domain.

how can i add ssl to mapped domain?

i know cpanel account can have one ssl. so how can you handle this?

so how can i add ssl to all mapped domain that i need?