These Athenian 'ox-buyers' (again at beta 387), probably a board of ten per year, are attested in Demosthenes 21.171 (n. 1 below) and in epigraphical evidence from the same period (C4 BCE).
[1] Similarly in other lexica. The only known holder of this post is Meidias, the enemy of Demosthenes (see Demosthenes 21.171), who served as general (strategos) at least twice. [Meidias' generalships are not listed in R. Develin, Athenian Officials 684-321 BC (Cambridge 1989) no.1921, but see L.A. Tritle, "A Missing Athenian General: Meidias Kephisodorou Anagyrasios," Athenaeum 70.2 (1992) 487-494, who draws attention to evidence for a plurality of Meidias' 'generalships' (strategiai) at Demosthenes 21.148.]
[2] The Greek here is ambiguous, as either strathgou/s or bow/nas may be the subject of the verb xeirotonei=sqai. The alternative reading, then, is: "since they say that ox-buyers were very likely to be elected generals."