I don't think IWC has a suitable bracelet...
Hi Mark,
This is without checking, but if I recall the lug width of the new Vintage Collection Aquatimer is either 21 mm or 22mm. If so, then IWC doesn't make any bracelets that wide, except for models with proprietary lugs like the Jumbo Ingenieur (which actually has a smaller lug width but is flared beyond the horns).
However, what I don't know is whether the new Da Vinci steel bracelet might fit. It would be very expensive and I don't believe it is separately available yet.
There are some aftermarket steel bracelets available at 22mm. if I recall, that really are meant for Panerai. You probably could find one at a reasonable cost.
But, really, you might want to try to rubber strap. It is just excellent --a modern-day version of the original. I also use the rubber-strap Cousteau Aquatimer as my swimming watch and it's very nice.
If others have further or corrected information here, please let us know,
Regards,
Michael