I bought a patch with a velcro backing and then used liquid stitch to hold the velcro onto the cooler. It's holding just fine although I wouldn't trust it much on something repeatedly going through a washing machine.

Dritz 395 Original Liquid Stitch, 2-Fluid Ounce https://smile.amazon.com/dp/B0019KHG3E/ref=cm_sw_r_apan_glt_i_9KE51Z3PWTP5C0FCEJ71?_encoding=UTF8&psc=1