For good quality, see Pomona:
Female BNC to double banana plug50 Ohm BNC feed-through terminatorThe BNC male to dual female banana jack adapter you post is the opposite of the first. And a BNC female to RCA is something you might use to connect a scope to an analog audio device, not to measure a power supply. I personally would not worry about the quality of cheap BNC to banana jack or plug adapters, it is not like these are for high frequency use anyhow.
For a much cheaper feed-through terminator that seemed to perform decently (but note that they may have changed construction):
https://www.eevblog.com/forum/testgear/banggood-50-ohm-bnc-feed-through-terminator-a-quick-review/The last thing Dave shows is a probe tip to BNC adapter. These often come with good probes. Some probe manufacturers (e.g. Keysight, Tektronix, Lecroy, PMK, Pomona, Probemaster) may also offer them for sale as optional accessory. If they do not, then you may have to find another one from a probe that has the same dimensions. These dimensions are not standard, so double check them.