Private packs w/washable sleeves: https://privatepacks.com/products/private-packs
Shorts example: https://www.amazon.com/dp/B097RSDDD5/ref=cm_sw_r_cp_api_glt_fabc_J6VN88BRZC7SK1Q4ZXP4?_encoding=UTF8&psc=1
Target ice pack (sleeve is too thick on this, I use sleeves from private packs as they are very stretchy): https://www.target.com/p/hot-cold-reusable-pack-12-24oz-up-38-up-8482/-/A-14517968