Sell newsletter ad slots direct. Sponsors book, pay, done.
Copy the embed code and paste it in your website to display that your product was featured.
<a href="https://toplistly.com/products/sponsonizer-com?ref=sponsonizer.com" target="_blank">
<img src="https://media.toplistly.com/embed/featured.png" alt="Sponsonizer Featured on Toplistly" style="max-width:222px; max-height:50px;"/>
</a>