Bintel has some 303mm ($80) rings which should fit a 10" tube, measure it.
Andrews has them as well, prolly for less dollars, but I can't find em
I'd go side by side there else you'll have to add more counterweights.
I have
one of these and it works fine. V series is for Vixen style bars.
You may need another couterweight anyway, suck it and see.