Slip-on shoes for my boyfriend?

My boyfriend (20 years old) has this really old pair of Nike brown suede slip on shoes and they definitely dont make them anymore. He is always dressed down. I am looking for something suede, very casual, that can be worn with sweatpants or jeans. I was looking at some uggs slippers with soles but was wondering if that was dumb or if anyone else had any ideas?! THANKS SO MUCH!