What should u do if u don’t have enough clean undershirts for Yom tov?
We are not allowed to do laundry on Col Hamoed even if it is for Yom Tov use. The reason for this is so that we will do enough laundry before Yom Tov. The option therefore would be to buy more for Yom Tov on Chol Hamoed.
O:CH 534-1, M:B 534 Halachos of Chol Hamoed chap. 4 ftnt. 32