Man, those wire colors, the blue painter tape to identify the wire number, etc., could be from my rear panel.
Two things:
1) You say "fuse block", is that meaning blade fuses? If so, I'm assuming you're trying to replace the actual 1/4" terminal that the blade fits into??
2) Per the relay, that's the same white plastic piece mine have. Is that from the weather proof type micro 5 pin relay socket?
As you have probably already done, I did some searching. This is the only link to a socket with that type of plastic retainer that I could find.
https://www.newark.com/te-connectivi...ctromechanical
Personally, if you're trying to find individual relay socket parts, I think you would be better off buying a new socket that's either already wired, or one that comes with the pins to wire up yourself.
https://www.aliexpress.com/i/32859642927.html
I hope this helps.