Thanks. I know these sources already, I was more digging into the internet archives, if somebody have trade data (or even average or close daily data) from BTC-E, where LTC have started trading on LTC/USD and LTC/BTC markets.
Such data can also be found on investing.com, for example. Here you can choose which pair you are interested in and also the exchange: 
(There is also an "Litecoin Index")
After selection you can switch to "Historical Data" here and specify the time window:
Afterwards, the data would also be downloadable there if you have an investing.com account. I tried this for Bittrex only, the data goes back to 2017, but other exchanges may offer more historical data.