I made a great decision the other day, I purchased a circa 1930 Conn alto horn. It was just sitting on the wall wanting to come home.

I got a mouthpiece with it, but it is not an alto horn / tenor horn mouthpiece.

My understanding is that this horn has a conn #3 bore, which is 0.5 inches.

Does anyone know which modern alto horn or tenor horn mouthpieces will best fit it (in terms of shank size)?

The main ones seem to be:
Dennis Wick heritage
Dennis Wick classic series
Bach
Yamaha

The yamaha 301 has a smaller bore than this instrument was advertised as having.

I have also seen a post saying that a Bach mouthpiece was too large for an old Conn horn.

The mouthpiece that I currently have is a patrick hybrid trumpet. It is great for the high notes, but its rim is really much too small.

Any other impressions of these mouthpieces would be helpful, as they are not in stock locally, so I would have to order one.