Main Update:
The DRAM and Flash chips have now arrived, so I can start production of the upgrades again.
Very long secondary update:
I also ordered some of a different DRAM chip to try out and the results are interesting.
These other chips are 8k refresh, 13x9 row and column arrangement, self refresh (I'll call them the 8k chips). The previously tested-working chips are 4k refresh, 12x10 row and column arrangement, self refresh (will call them the 4k chips).
These 8k DRAM chips work too, and report the same 3976k System RAM as the 4k chips. I had hoped that the eMate system would be able to 'pick up' the extra capacity and result in a full 16 megabytes of DRAM - but that didn't work out. Makes me wonder whether a change in the eMate ROM could unlock the extra capacity.
The 8k chips have a row and column matrix which is called out specifically as supported by the CL-PS7110 (successor to the CL-PS7010 in the eMate). The CL-PS7110 datasheet also says that it can support up to 256 megabytes of DRAM. I'd love to update the ROM to make the eMate work with these 8k chips but that's a rabbit hole which might be too deep for me.