A team I worked on tried to buy browsing histories for specific sites about 10 years ago. NetZero was selling them from their free dialup customers, but the data was not that useful as the demographics of users was super skewed. All the ISPs that people tend to think are evil absolutely refused to even entertain the idea. One of them even lectured our PM on privacy and ethics for a few minutes before ending the call.

You can buy advertising profiles (or access to them) but this not really useful for things that are not directly advertising as it is super aggregated. In general the ISP data is less valuable since so much of the web has moved to using SSL.

I don't know much about how this has changed over the last couple of years but maybe someone else can chime in.