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It would be extremely difficult to observe something that far away from the sun, no matter how voluminous it is. I'm not going to scorn at the idea of a blackhole, but I wonder what process can crush that much mass into such a volume. I don't think it's massive enough to suffer a gravitational collapse.

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Primordial black holes can theoretically be much smaller than those formed in the usual way from collapsed stars or neutron star mergers, etc, because the early universe was dense with matter already and perturbations could have caused gravitational collapses for arbitrary volumes. I don't think we've observed any directly, which would be hard as small low-emission masses. They're still a potential piece of the dark matter missing-mass puzzle.

Primordial black holes are black holes that formed right after the big bang. Basically areas where gravity caused the extremely dense matter of the universe's first instants to collapse into black holes before expansion could pull it apart. Their existence has been hypothesized but not confirmed (or definitively rejected) so far.

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