Pinnacle doesn't offer stock prices. I find them a great source for other things - forex, stats on S&P dividends and earnings, interest rates, etc.

Trying the same post on the Mechanical Investing board would probably get you a good set of suggestions. Likely including how to continue to get data from Yahoo.

My advice would be to focus on the best available quality of handling of dividends and spinoffs, not the price of the subscription or simplicity of use.

Not what you asked for, but one non-source of data with dividend reinvestment is a chart at stockcharts.com.
By default all their graphs include reinvested dividends. You can see price-only charts by putting "_" before a ticker. I use the "ratio of two securities" feature a lot, e.g., to check to see if Berkshire is sliding behind or pulling ahead of the S&P, you'd do a chart of BRK/B:SPY (almost exactly a tie in the last 2.5 years)
I suppose you could then run their graph through webplotdigitizer!

Jim