Do na-adjectives have an attributive negative form?

Question

Assuming present tense, we can use i-adjectives in an attributive context both in the affirmative form:

高い　椅子　が　あります　- there's an expensive chair

And in the negative form:

高くない　椅子　が　あります　- there's an inexpensive chair

---

I know we can use na-adjectives similarly in the affirmative form:

綺麗な　人　が　います　- there's a pretty person

But for the life of me I can't find any info on whether using na-adjectives in the negative form is allowed in an attributive context (i.e. modifying a noun rather than as a predicative with a copula). So is the following grammatical?

綺麗じゃない　人　が　います　- there's a non-pretty person

Answer 1

Your guessed-at negative attributive is perfectly correct. The only caveat I'd add is that じゃ is a somewhat-informal contraction for では, and thus you should probably use the full では form in any formal spoken or written context.

綺麗[じゃ]{●}ない　人　が　います
          ↓
綺麗[で]{●}[は]{●}ない　人　が　います

Happy studying!

Answer 2

Although the name might scare people away, Japanesewithanime actually has a really in-depth post that covers this topic. I'll just quote the relevant part discussing why your guess was right, but there's a ton more information, so you might want to read through it.

The na of na-adjectives is actually a copula. The prenominal copula, or attributive copula.

Basically, da だ is the copula you use in an independent clause, while na な is the copula you use in an attributive clause, also called adjectival clause. A clause that describes nouns.

But there isn't a negative form of な, so you have to go back to だ.

The negative form of na-adjectives is literally just replacing the normal copula by a negative copula such as denai でない, dewanai ではない or its contraction, janai じゃない.

He includes a link talking about the difference in usage between ではない and でない