OK I found one!
This may help you Aunt Betty. After a few phone calls and a lot of web surfing I founfd the answer. The Burris speed bead is no longer made for the 390 and Cabelas hasn't sold one for a 390 since 2009. I contacted Beretta and they gave me the correct Burris Part number (300246). I then called Burris and they still have the mount in stock. Then another call to Cabelas and they're going to order one for me.
I want it for a couple reasons. First it will work as a turkey site. Second my left eye doesn't work correctly so I have to close it when shooting. Third stance and form are a lot easier to achieve on a range than a swamp. That's what the Speed Bead is saposed to aid in. I know it's a comercial but go to their web site and check it out. I may be paying for a gimic but you never know until you try. I've gotten a lot of smart remarks on the web about them but nobody that has tried one.
I met three hunters who have them and love then. I figured I'd get one with the change I've saved. I'll post the results when I get it.