That's what weird thing about Sony, they don't have a separate recovery image partition.
Most Xperia custom ROMs include their own boot.img(with recovery in it) so that's covered.
Tapatalked from my Xperia P
My Nexus 5 mods for PA
My Family's Android devices - xperia P, xperia SP, xperia TX, moto G, and nexus 5