Yes, Norman 200B's and 400B's had a bare bulb with the option of a round reflector or mounting of a slip on speed ring to mount a soft box or similar modifier. The Normans were a high end pack and head unit ( I have one old 200B that I restored).

So even many years old they may not come cheap.

Why not consider the possibilty of masking off the edges of the 35mm form factor reflector, or just add a diffuser and live with the stiop or more of brightness loss.