The Commodore Amiga 3000 allows for up to 16mb of Fast RAM expansion via 32 ZIP-20 sockets. The age and relative rarity of these chips compared to other RAM expansion of the era makes these hard to find, especially since they tend to be listed by part number rather than specification.
When looking for these chips, one is looking for up to 32 80ns ZIPs in groups of 8. They can either be 1Mx4 (for 16mb) or 256kx4 (for 4mb). They can be static column or page mode chips. Page mode is easier to find. Static column allows for burst memory access which can provide a 10% speed boost.
This page provides some part number options. It is not exhaustive, and not all of these have been tested.