You need to determine how much of the 33.2mm dial shows through the rehaut opening. A replacement dial does not have to fit all the way to the edges of the dial seat in the case. The dial will be held in place by the movement and can have a gap to the case walls. The goals are for its edges to be hidden under the rehaut, and its minute track not to be inset too much.
So to answer your question you need to remove the movement and dial and measure the inside diameter of the rehaut opening. Then add at least .2 - .3mm to make sure the dial edges stay hidden. Then find a dial that will fit with a minute track that isn't a ridiculous distance away from the dial edge.
Failing that, it is possible to create a spacer that will effectively decrease the diameter of the rehaut opening. But it needs to be quite precise in its dimensions so would need to be hand (machine) made like with a dremel minimally or a lathe ideally.
The simplest example would be a perfectly fitted washer to the edges of the dial seat with an inner diameter extending inside of the rehaut opening and stopping just outside of the dial minute track. It would have to be very thin so as not to recess the dial and movement down too much due to cosmetic and stem placement ramifications. And of course it would be visible next to the dial so there's that. it could be painted or otherwise colored somehow, etc. It could also be brushed or polished stainless steel to match or complement the rehaut.
A more sophisticated approach wound be a custom made movement holder whose dial side inner lip was made to create a border around and slightly overlapping the dial edge. I have seen examples of these efforts being done. They are always noticeable and you will have to decide if that's acceptable.
Another method would be to epoxy a very thin plate (a thinned old dial stripped of markers and feet) to the underside of your smaller dial. This would leave you with a slight stairstep dial edge. Of course the plate edges would need to be matched somehow, and the replacement dial edge might need to be cleaned up a little (notch at 3 o'clock sanded away if present). Lots of dials have a stairstep edge, including the new Rolex 126x dials. The stairstep is not visible though, the cases are perfectly machined to fit them.
Whatever solution you might concoct to fit a dial smaller that the rehaut opening will take some careful custom work and won't look seamless. Hardly worth the effort IMO.
