Gen-Mar Handlebar Risers are machined aluminum spacers that raise the stock handle bars by about 3/4″, slightly elevating your riding position. They are available from Gen-Mar Manufacturing.
Installation of the risers is simple (see photo journal) with one possible exception. Raising the right handlebar uses up slack in the front brake line. Most GPZ list members reported this was not a problem but some bikes (including mine) didn’t have enough slack and required the front brake line be replaced.
Photo journal of the installation procedure is here.