Now, as far as I'm aware, Stanley never offered an Ovolo cutter for the #45 or later brethren, although there were (eventually) six sizes of Quarter Hollow for the #55 - cutter numbers 61-66. Record, on the other hand, from the get-go offered three sizes of Ovolo cutter amongst their additional cutters. Now I have a later model #405 and that had a couple of Ovolos included instead of the less useful Sash cutter - it must have come that way because the oh-so-tacky plastic wallet helpfully labels the content. An excellent move on Record's part, in my opinion, and I bless them for it - the Ovolo inclusion, not the tacky plastic wallet... Because they work really well, as you can see in the last section of this ancient video of mine:
"Great," I hear you #45 owners cry, "I'll look out for a Record Ovolo cutter and try it in my Stanley plane." Ah, might want to hold your horses there. Here's a comparison of the Record #405 using its provided cutter, and the same cutter in a #45: (you'll need to click on it to see the large image)
Bet you thought the Stanley and the Record were near-as-dammit identical too, didn't you? So how about the #55 cutters? All Stanley right? That's going to work. Um...
Of course this shouldn't surprise us that much. With its adjustable depth skate and so forth, the #55 cutter is able to be designed with the shallowest part of the cut handled by the main body skate and the deepest by the depth adjustable skate. In contrast, the #405 skate is lined up with the deepest part of the cut and the rest of the cutter has to make its own arrangements. And yes, you'd think that'd be a disaster. The slightly stubbier profile helps, I think.
However, having dashed all you #45 owners' hopes, it seems to me an Ovolo cutter reground in the right places to provide the necessary clearance for the #45 should work. Or one ground from scratch, of course. I have no reason to do it (she says, hugging her #405 to her person and never letting go) and I haven't heard back from my correspondent to see if he's tried it either, but if anyone has - or is inspired to give it a go - I'd be interested to hear how you got on.
Naturally, when talking about details of manufacture of combination planes, my usual caveats apply - I can't guarantee that any of this applies to any examples of these planes and cutters other than the ones I have.