Cheapest "sold for Threadripper X399" 32GB quad channel RAM kit I could find.
CORSAIR Vengeance LPX 32GB (4 x 8GB) 288-Pin DDR4 SDRAM DDR4 2666 (PC4 21300) memory kit for DDR4 Systems Model CMK32GX4M4A2666C16R
DDR4 2666 (PC4 21300)
Timing 16-18-18-35
CAS Latency 16
Voltage 1.2V
Note that the three colour choices make up more than 10 units.
I wouldn't go for sub-3000 RAM anymore. 3000 C16 is the sweet spot I reckon.