Historical data for 3 month and 6 month lows for NYSE or Nasdaq

user749798
I'm trying to find the historical data for 3 month or 6 month lows. Thinkorswim has it (NYLO3M) and barcharts.com has it (M3LN) but they don't match...and thinkorswim only goes back to 2012. Does anyone know of another source where I could get this data?