put in a plug for (someone or something)

To speak very highly of or enthusiastically endorse someone or something, as a means of marketing, advertising, or professionally recommending them or it. I was really impressed with your work, so I'd be more than happy to put in a plug for you the next time someone asks me for a mechanic. As part of their sponsorship deal, we'll need to put in a plug for the product during your radio show.