group 31 and 29 are so close in size we always install group 31 box. Here is a link.

https://www.amazon.com/SeaSense-50090675-31M-Battery-Box/dp/B001GJ36DC/ref=sr_1_7?dchild=1&gclid=Cj0KCQjwnJaKBhDgARIsAHmvz6ezulzgxbEohndMqW-XvOK9wTn8BxoCzdD9j0KQ-Uirn5XRydG1wRkaAnh3EALw_wcB&hvadid=174245266796&hvdev=c&hvlocphy=9017487&hvnetw=g&hvqmt=e&hvrand=363674149749397973&hvtargid=kwd-3120991897&hydadcr=7494_9322280&keywords=group+31+battery+box&qid=1632004361&sr=8-7