22.2 mm clamp handlebars did exist once upon a time, and are still to be found occasionally, though not cheap:
Hilary Stone has a few.
Hilary Stone Classic Corner Handlebars
But you are not likely to find a wider bar than the one you have. Handlebar widths are one of many aspects of bicycle fitment that change with fashions; I'm guessing your bike is from a time when narrow bars were preferred. I strongly suggest you keep the old bar and stem together; if they are not functional for you, just get a new bar and stem (not
too new, though!). But keep the old ones so you can return the bike to 'collectible' condition if you wish.
Were it mine, I'd probably just ride it with the narrow bar... get that whole vintage bike experience.