Not something I have experience with, unfortunately. I had a look around Google, and it seems there are software solutions available for some of the Sage packages, but they vary from around £300-500. The most common seem to be
Connect .
However... there may be another way to go about it. I'm not familiar with any Sage products (I HATE accounts!), but if you have the option to import data into your Sage package, maybe as a CSV (comma seperated values) file, it *should* be relatively simple to use PHP to export stock data from a MySQL Database to a CSV file (or another importable format). It wouldn't be as elegant as having a fully integrated solution, but I reckon it'd be cheaper.