FurHaven Soft-Sided Dog & Cat Playpen, Portable Foldable Indoor & Outdoor Pet Playpen with Mesh Windows & Zippered Door, Gray, Small

We used this when we had a baby kitten- https://www.amazon.com/dp/B01IS5TGB2?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_4&th=1 If you keep the door portion unzipped the mama cat should be able to get out.