v-Color DDR4 64GB (2 x 32GB) Hynix IC 2933MHz(PC3-23400) R-DIMM for Apple Mac Pro 2019 ECC Registered DIMM Dual Rank 2Rx8 1.2V CL21 Server Memory Ram Module Upgrade (VHA21ASDRAG8T-BG29RD) at Amazon.com
2019 - 16" Touch Bar MacBook Pro, 2.6GHz Six Core i7 Processor, 16GB R – The Apple Xchange - Preowned Apple Products and Services
The next MacBook Pros may pair Apple silicon with 64GB of RAM | Engadget