Alex,

I don't know about Miami, but I have used Complete Yacht Services in Fort Lauderdale for many parts for Yanmar engines over the years.  A good business and they know the engines well. They also maintain a good stock.  Pretty much all the official dealers will be pretty close on price.

completeyachtservice.net

For those of us with Volvo TMD22 engines, these guys are a Perkins dealer as well, and most parts for the Volvo are identical with Perkins at a significant cost savings.

Bill Kinney
SM160, Harmonie
Norfolk, VA, USA