Kit part numbers are:
HWGXXX0002218S for Shimano
HWGXXX00S3382S for SRAM (XD)
Kits will include both caps, part numbers are from the DT Swiss 2019 Techbook.
If you’d asked about a week ago you could have got them (either version) from bike-components for about $40 delivered as they had a free shipping promotion.