I sent Ruger an email yesterday asking about buying a taller front sight and when I checked my email just now, they had responded.
They won't sell any parts for old models which have not been converted to the new style with transfer bar.
But.... I can return it for a free conversion and they will install a proper front sight which, I assume I will pay for.
They are sending me a shipping label and RGA.
Thanks for the help but it appears Ruger will solve my problem.