People online asking about fragments of Papias, who knew the apostles, lead you to obscure authors. I had heard the name of Theophylact before, but never knew much about him until today.
The biblical commentaries of Theophylact — who was Byzantine Archbishop of Bulgaria — fill four volumes of Migne, 123-6. Somewhere in one of them is a quotation from Papias, discussing the fate of Judas. It seems reasonable that this is in the commentary on Acts, in vol. 125, and so indeed it is, on cols. 521C-523D. The “commentary” seems mainly to be a catena, in fact, as might be expected. Chrysostom Press has produced an English translation of his commentary on the gospels; I don’t know of an English translation of the commentary on Acts.
Here are the relevant portions of Migne: