Overlays are not a common thing, since
poker sites tend to adjust the guaranties to avoid them. ACR and
888 Poker sometimes have them but only at certain times of day, where volume is low. If you play during peak hours, you can pretty much forget about finding overlays, and they are also less common during weekends. Special events are more likely to see overlays, since poker sites have less data to estimate player interest, and sometimes sites also let satellites run with overlays for long periods of time to beef up the target tournaments. But even if the satellite is a micro buyin, the target tournament is not, so you need a decent
bankroll to play these.