Custom units will provide maximum use for the space you have.

Would like to see a pic? Can you use two 32" vanities or one longer vanity? Regarding the floor, there may be a way to change the floor in that area. Remove the flooring in that space. Border the area with a contrast tile or wood strip and new flooring. Fill in the rest of the space with a co-ordinate tile or flooring to appear that it was in an original design plan. Then you would not need vanities that go to the floor and can be mounted on legs.
I hope I'm getting the vision of the space and understand the question.

There are many ways to provide for your storage needs. In the absence of a floor plan or photo, it is difficult to be creative and offer ideas. You seem to have settled on your solution already--what are you looking for frin Houzz?

I have limited space and that is why need two vanities on each side of a sliding door that goes into my closet. the plumbing has to go under the new floor and come up under the vanity as the back wall will have the sliding door on it. That is why it is a challenge to find vanities that will work. I know that I could use 32' but want to maximize space and have the room for a 36 on one side of wall. have been checking the Houzz and internet sites and hard to find vanities that also have drawers with cabinents space.

Please post a pic : )

In the smaller size vanities, there will be no space or very little for storage. I'm guessing, but I would use the same size vanities (32") on each side of the door. Then find other solutions for storage.