Where to find offers: the affiliate networks are your marketplace. ShareASale, CJ and Impact for mainstream brands, ClickBank and Digistore24 for digital products where the commissions are much higher. Sign up free and browse by category.
What actually converts on Pinterest is visual, buy-intent stuff, so home, beauty, fashion, food and DIY tend to do the heavy lifting. I'd point pins at your own content rather than straight at the offer, you keep the tracking and the traffic even if the affiliate link dies. Chasing trends is a trap imo, evergreen niches compound. What are you posting about now, that decides which networks are worth your time.