shabbat - Do people who don't eat gebrokts have any reason to say "Borei Minei Mezonot" during Pesach?

This may sound like a trivial question, but I'm curious.

Many Chasidim do not eat gebrokts during Pesach. So all the Pesach cakes are made from potato starch which makes them shehakol. And they only eat shmurah matzah which is hamotzi. Is there anything during the week of Pesach that they can make the bracha borei min mezonot on?

Someone in my neighborhood wants to make Se'udah shlishit on Shabbos during Pesach in shul to accommodate Chasidim. He doesn't want to bring matzot because it requires washing, and the shul kitchen is closed so there's really no convenient sink to wash. (He is averse to using the rest room sink.) He also insists that there be mezonot at Se'udah Shlishit. What can he use to accommodate the Chasidim?

Edit based on comments

Let's assume that the Chasidim do not eat any kitniyot either in whole form or as a processed product. So, that would exclude rice cakes / matzot.