Firstly, there are two labs in the Castelia Sewers; the one that is mentioned, but also another lab which is closer to the staircase leading to the Alley area of Castelia City, containing a male scientist. I think that this can only be done in Spring and Summer though, when you can surf in the sewers.
Secondly, in the part of the Virbank Complex connected directly to the city, there is a roughneck wjho will trade you a Great Ball for a Pokéball once a day. He is down a staircase standing in a corner next to the river to the right when you cross the boundary line between Virbank City and Virbank Complex. I feel this should also be added to the Daily and Weekly Events page.
Errors: GK/LK base power is off. It should be 10.0 - 24.9, 25.0 - 49.9, etc... and King's Rock has a 10% Flinch Chance not 11.something
Links: http://www.serebii.net/attackdex-bw/lowkick.shtml http://www.serebii.net/attackdex-bw/grassknot.shtml http://www.serebii.net/itemdex/kingsrock.shtml