Here's what I know:
1. LSJ says that that the masculine form CHROS occurs "later" and cites three texts.
later masc. XHROS widower,
Arist. HA 612b34 (of birds),
Call. Epigr. 17,
Gramm. post Hdn. Epim. 286
2. A search on Perseus reveals 19 "possible" occurrences in the primary texts, but most of these use the feminine form; the exceptions are all in Strabo, who is in the Hellenistic period. See these results, if interested:
"http://www.perseus.tufts.edu/cgi-bin/wordsearch?lookup=xh/ra&lang=Greek&corpus=2.0"
That's all I know...
Jonathan