Clownfish like to pick their own mates.
I've tried making arranged marriages for clowns, and often those relationships turn into a total knockdown drag out fights to the death, kinda like human relationships turns out.
It can work out, but you should be prepared to remove or separate any prospective mates you try to add. A lot of people avoid trying to find a new mate, trade in the widow/ widower and get a new mated pair from the LFS. Good luck.
Reading your post again, If you add a new clown, get a larger female for the little male, as since she is new to the tank and he is small, the chances of a successful pairing are better than if you had lost your male and you are now trying to introduce a smaller fish into an established territory.