I recommend getting 700ml jars (ca. 24oz/1.5 pint) to make sure you’ll have a satisfying lunch. Most popular and certainly well suited for Salads in a Jar are classic “Mason Jars”. You can buy them here on Amazon and in well-stocked home improvement stores. Personally I use empty pickles jars. Those a big and “for free”. It meant I had to eat many pickles though, haha. And of course I get minus points in the category of “style”.