Trying to market to large office buildings... How...?

Our company manufactures and sells flower vending machines to local florists. We find it best to find suitable locations for the vending machines first, then contact local florists in the area to see which ones want to buy a machine and place them in these locations. One venue we are trying to get into is large office building lobbies. We are based in Louisiana but we sell these nationwide. How can I find out what large office buildings are (for example) in Los Angeles and who to contact about trying to lease space in the lobby for our flower vending machine.

I tried contacting some realtors but they all say the amount of space we want to lease is too small for them to consider and that we must talk to the building ower/leasing people directly. Finding these buildings/owners/leasing people from out of state is our challenge.

Anyone have any ideas on how we can locate and contact these people by phone?