I've personally found that every Ruckus AP's I've used except the R710 (which is PoE+) is happy with generic 802.3af POE injectors, including inexpensive ones you find on Amazon.
Of course, low-cost ones may mean you need to replace injectors more frequently over the course of ownership which can be inconvenient and cause downtime....
But yes, they should work. The R310 only requires 802.3af power.