Perhaps it would be helpful to review some of the examples listed in BDAG under the "public notice" option to demonstrate that these involve something which is indeed "previously written," drawn, painted, etc. That is, it is not used in a metaphorical sense.
Josephus, Against Apion 2.252 -
(252) The painters also, and statuaries of Greece, had herein great power, as each of them could contrive a shape [proper for a god]; the one to be formed out of clay, and the other by making a bare picture of such a one; but those workmen that were principally admired, had the use of ivory and of gold as the constant materials for their new statues1
Plutarch, Demetrius 46.5 (which BDAG lists as 46.10) -
But nevertheless they would have their pleasantries; and one of them wrote up in front of the tent of Demetrius the opening words of the ‘Oedipus,’ slightly changed:—2
Plutarch, Moralia 408e (which BDAG lists as 408d) -
if the opinion which he holds about the god is such that he can accept and admire the maxims of of the Wise Men inscribed (progegrammena) here, ‘Know thyself’ and ‘Avoid extremes3
Again, the common treatment of prographō in Galatians 3:1 as (unambiguously) metaphorical is apparently without precedent, per biblical or Greco-Roman literature [prove me wrong!]. Hence, I contend that we need to try harder to find a non-metaphorical approach for translating this passage. Perhaps a more appropriate translation might be
O foolish Galatians! … What was previously written concerning Jesus Christ’s crucifixion was presented before your eyes.4
And what might this be referring to? This appears to refer to something like a Gospel, such as Matthew. Therefore, I offer the following as "my answer" to the question, unless someone can come up with some OT options.
And they spit on him and took the reed and struck him on the head. And when they had mocked him, they stripped him of the robe and put his own clothes on him and led him away to crucify him. (Matthew 27:30–31 ESV)
1Flavius Josephus, The Works of Josephus: Complete and Unabridged, trans. William Whiston (Peabody: Hendrickson, 1987), 809.
2Plutarch, Plutarch’s Lives, trans. Bernadotte Perrin (Medford, MA: Harvard University Press, 1920).
3Plutarch, Plutarch’s Moralia, trans. Frank Cole Babbitt (Cambridge, MA: Harvard University Press, 1969).
4Daniel Moore and Phil Fernandes, A Trustworthy Gospel: Arguments for an Early Date for Matthew’s Gospel (Eugene, Oregon: Wipf and Stock, 2024), 60.