Well, given the tone of their recent conversations about Ianto wanting to try more, why not have some fun adding to his inventory!
"Mmm, it'll definitely be worth it," he says warmly, pleasure spreading through him just watching Ianto getting his hands on it. "In the meantime..." he brings out a rather less mean looped leather slapper and hands that over too for inspection. "I thought we might try this first. To be honest, it's not that different from just using a belt, but since I was procuring stock I thought we might as well have something purpose made!"
Even if he does enjoy the hell out of perverting everyday items too.