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