Pelican 1650 alternative foam inserts?

[UmiKaibutsu]

I bought a Pelican 1650 without foam. Its basically the size of a large suitcase, with dimensions at 62" total so it is allowed as checked baggage without extra fees, albeit heavy empty.

I figured I could get foam elsewhere, aftermarket. Does anyone know what the alternatives are?

I didn't buy foam as I know it will likely be a multi-usage case, so the Pelican foam would be wasteful. I was curious what other creative ideas people have had for this sort of thing.