from maya import cmds
import maya.mel as mel

mesh = cmds.ls(sl=True)
cmds.select(cmds.skinCluster(mesh[0], query=True, inf=True), replace=True)
joints = cmds.ls(sl=True)
bindgrp = [mesh[1]]
bindgrp.extend(joints)
newskinCluster = cmds.skinCluster(bindgrp, toSelectedBones=True)[0]
origSkincluster = mel.eval('findRelatedSkinCluster '+mesh[0])

#Wrap new mesh to old mesh.
cmds.copySkinWeights(sourceSkin=origSkincluster,destinationSkin= newskinCluster, noMirror=True, surfaceAssociation='closestPoint', influenceAssociation='oneToOne')
cmds.select(mesh[1])

print 'Done'