@R.M I have started with this `
Clear[colorbar]
colorbar[colorFunction_: Automatic, divs_: 150] :=
DensityPlot[y, {x, 0, .1}, {y, 0, 1}, AspectRatio -> Automatic,
PlotRangePadding -> 0, PlotPoints -> {2, divs}, MaxRecursion -> 0,
FrameTicks -> {None, Automatic, None, None},
ColorFunction -> colorFunction]
ColorBar[plot_, cf_: "Heat"] :=
With[{size = 300}, Row[Show[#, ImageSize -> {Automatic, size},
ImagePadding -> 20] & /@ {plot, colorbar[cf]}]]
ContourPlot[2 Sin[Norm[{x, y}]], {x, 0, 10}, {y, 0, 10}, ColorFunction -> "Heat"] // ColorBar[#, "Heat"] &`