Clients who do their own research often find reference to very expensive market research reports. Often, these items are not available on the shelves of your local public or university library. (They're certainly beyond the budget for our library, too.)
However, there is a site that your clients might consider visiting in these circumstances. It's www.marketresearch.com. This site makes available for sale reports from many market research firms. Of course, they'd rather your clients buy the whole report. However, they also allow them to buy "by the slice".
When there, your client can search for a given report. If it's in their database, they can then search within the report for a given word or phrase. They'll then get results that show them the context of the report in which that word or phrase is used. If only one or two instances fit your client's needs, then they can buy just that chapter. It still won't be super cheap, but they'll likely be paying only hundreds of dollars, instead of many thousands for the whole report.
Something to consider . . .