There is Vagambhrini from RV 10.125.
I'm not sure if Apala(8.91)is considered a rishi or not although in the hymn she has the kind of visionary experience attributed to Rishis.
There are others who are mentioned or who speak and thus could be considered rishis but I don't have the Anukramini close to hand and I'm not sure what the tradition is regarding them.
They include Romasha, Lopamudra, Kadru, Visvavara, Ghosha, Juhu, Paulomi, Yami, Indrani, Savitri, and Devayani according to Wikipedia. https://en.wikipedia.org/wiki/Rishi
Hopefully, others are better informed about this. It's an interesting question.
Best,
Dean