Comibne two different domain SSL certificates to single certificate

Suppose, I have two domain 1. example1.com 2. example2.com I have SSL certificates for this two domain. For example1.com example1.crt and example1.key and for example2.com example2.crt and example2.key Is there a way to combine these two certificates to one crt and one key file ? I want to use the single certificate in the classic load balancer.

Thanks