Hi Chrys
Depends on how much you want to raise the rings from the Vixen bar. If only 10 or 20 mm lift is needed then buy something like this ; -
https://www.ebay.com.au/itm/22528521...AAAOSwJ~5b8I7g or
https://www.ebay.com.au/itm/22494865...kAAOSwzVxfGBn5
Then cut to the length you want and drill the holes in the appropriate places. Hope this helps.