I'm trying to develop a function which 3D plot would have a buttocks like shape.

Several days of searching the web and a dozen my of own attempts to solve the issue have brought nothing but two pitiful formulas below. They have some resemblance to the shape I want, though not quie. Could you help me to obtain a proper formula?

Here are those bad solutions I've got myself:

ParametricPlot3D[{Sin[y] Sqrt[1 - (Abs[x] - 1)^2], 
  Cos[y] Sqrt[1 - (Abs[x] - 1)^2], x}, {x, -10, 10}, {y, -3 Pi, 3 Pi},
  AspectRatio -> Automatic] 

and

Plot3D[((2 Sqrt[30 - x^2 - 2^-x]/3) + Sqrt[1 - (Abs[y] - 1)^2])/2,
   {x, -7, 7}, {y, -7, 7}, AspectRatio -> Automatic]

I'm trying to develop a function which 3D plot would have a buttocks like shape.

Several days of searching the web and a dozen my of own attempts to solve the issue have brought nothing but two pitiful formulas below. 

They have some resemblance to the shape I want, though not quite. 

Could you help me to obtain a proper formula?

Here are those bad solutions I've got myself:

ParametricPlot3D[{Sin[y] Sqrt[1 - (Abs[x] - 1)^2], 
  Cos[y] Sqrt[1 - (Abs[x] - 1)^2], x}, {x, -10, 10}, {y, -3 Pi, 3 Pi},
  AspectRatio -> Automatic] 

and the following:

Plot3D[((2 Sqrt[30 - x^2 - 2^-x]/3) + Sqrt[1 - (Abs[y] - 1)^2])/2,
   {x, -7, 7}, {y, -7, 7}, AspectRatio -> Automatic]