sou desu ne vs. sou desu na
 

Is it uncommon for the "na" particle to follow "desu"?

For example, I often hear in Japanese shows:
そうですね。 sou desu ne. So it is, isn't it?

But I don't think I've ever heard:
そうですな。 sou desu na. 　So it is, isn't it?

Thanks!

"そうですな" is verbal casual form used by elder and high-position male to another elder and high-position person.

I often heard this word in the movie, drama or novel but never in the real life.