Doing a few searches, I found this Mirafone 56L at Baltimore Brass. If you're not looking to spend a lot, you'll be hard pressed to find a better deal.

https://www.baltimorebrasscompany.com/p ... itone.aspx

I found a listing for a Mirafone 35W mouthpiece on ebay. I am not the seller. The seller is clueless as to what it is. I sent him a message telling him what it was but he still thinks it's for an Alto Trombone. This pics match my Mouthpiece exactly which is original to the Horn. https://www.ebay.com ...