This is what you are looking at https://www.ecpplastictrays.com/product/foam-cavity-tray-size-1-6-x-1-6/ Foam cavity tray turned up many results on google. They have lots of shapes and sizes What I like most about it is it is compressable so you can add a second piece of foam overtop, exceeding the height of your box. You can then press the lid closed, compressing the foam and sealing the coins in. I have no idea what this might cost or if they sell anything other than bulk quantities.
@AussieCollector thank you for the response. After long consideration I decided to go with SAFLIPs inserted in Supersafe pages, all housed in a Lighthouse Grande Binder. The deciding factor was that many of the inserts were very complete and I saw no reason to do them over. It won't look as nice and uniform as yours, but I think it will serve me well for the time being. Regards, LS (edit: I originally said Safe-T flips in error.)
I am sure most are aware of these... but I was not. I was looking at some options on eBay but you never know what the item from the "seller from China" will be like when it arrives. I just received these inexpensive Lighthouse trays today... they are more like tray liners as they are fairly flimsy if you fill them up with sestertius (for instance). Perfectly fine with denarii, etc. That is not to say they cheaply made.. for the money ($15 for a set of 2) they are of excellent quality. But they do need some support if you are to handle them often. My plan is to make a tray/drawer out of wood and use these as the liner. Then make a proper coin cabinet to hold multiple trays. I love Abafil but this is a more cost effective option for me and I can personalize the cabinet to my needs. They are available in various sized coin compartments. The price is right!