I just grab them off ebay. SAS drives are almost exclusively used in enterprise servers, so there’s fuck all demand for them on the used market. Buy a cheap PCIe SAS controller card and you’re good to go.
I use Unraid which doesn’t care at all about what types of drives you use, so you can mix and match into one huge array. I have 8x SAS and 2x SATA drives in one array.
I have strictly instructed my family, including my wife, that if I ever develop alzheimers I want to be euthanized. If I am sufficiently lucid at the point of diagnosis I will have no problem overdosing on something and going out in peace.