I don't have any examples however assuming you've got sphere collision detection working it's pretty trivial. If you don't have a working collision system then you need to read up on what that is and either write your own collision manager or integrate another collision system into irrlicht. I believe irrlicht has a collision system however I've never used it as I decided to go with bullet (there's sample code on these forums).
Once that's done it's simply a case of placing the sphere's at the position and orientation of the bones every frame after the bones have been transformed.