Really love these freezer packs by Magicfly. I love that they are large (7.4*7*.5) and thin. They dont last the whole day but they do last four to five hours. Even better they are 100 percent BPA free. They come in a package of six- two orange, two green and two blue.
https://www.amazon.com/gp/product/B0796SWB1Z/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc