HP Z600 Memory for V1 Mobo

Hi all, currently have 12 gig installed on my v1 system and wanting to add more memory as I am running W11 now. I do quite a bit of  VHS Video transfers and conversions. I am sure what I am needing is unregistered unbuffered ecc 2rx8 pc3-10600E. I recently bought some cheap ram but it appears they are registered and will not work. So, I am looking for some 4 gig chips (6) to upgrade my z600. Does anyone know (apart from E bay) where I might get them? or does anyone have them for sale. Thanks in advance