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I loved the sound of the Canadian Brass Chuck Daellenbach mouthpiece I formerly had, and the relatively small size worked well in many situations, like tuba quartet. It is aesthetically pleasing to look at, too; in fact I kept it on the shelf just as a sort of sculpture for months.

But the narrow rim and sharp edge didn't work with my chops. Is there a similar size Helleberg out there with a wider rim?

If you want one badly enough, you can pay Terry Warburton a few bills to make you one. I believe he made all the older CanBrass mouthpieces and should have them in his CNC lathe patterns. Send him a mouthpiece that has your ideal rim, and he can measure it and custom build you a ChuckD piece with that rim incorporated into it. I had him do something similar for me six years ago when I had him take the AJ mouthpiece, put a Mirafone C4 style rim on it, and add a few extra ounces (OK, pounds) of brass.
Of course, you could also try to go the Doug Elliot route of mixing and matching rims and cups, that has worked for many players.

The Laskey 28 Series is of similar size. I use a Canadian Brass mouthpiece now, but I was using the Laskey 28G, (Geib cup). The 28H is a Helleberg. I haven't seen or used one as I am now telling you about a $130 mp I am (sadly), not currently playing on, but it might be worth a gamble.