TubeNet

I believe Windsong sells visualizers: http://www.windsongpress.com/

Also, Baltimore Brass: http://www.baltimorebrass.net/index.php?cat=8

These days there are only two tuba rims that you can get. A brass one made by Floyd Cooley and a delrin version that I make. I buy the brass ones from Floyd and Hickey's, Dillon's and Baltimore Brass all buy the delrin ones from me. Get them from whoever is most convinient for you.

If you are concerned with rim size, One of my past teachers had a good option. Find a cheap mouthpiece with that rim size and just cut away the rest of the mouthpiece. There are cheap mouthpieces around, easily less than the 35 bucks for the only other metal vis. on the market.

I concur with the Kelly clear. Even if you decide you still can't see it and cut the rim off of it, you've still spent a lot less than another mouthpiece! Besides, then you have a mouthpiece for extremely hot or cold weather, or to take with you to try as an alternative when trying other tubas, etc.

At Tennessee Tech, they used to make a clear Lucite mouthpiece, the "Lloyd Long Mouthpiece." While it was great to use for cold weather, it was the best embouchure visualizer I have ever seen. Maybe you can find one on eBay... Maybe...

Rob, a buddy of mine used a band saw on an old Holtan Galaxy mouthpiece that I use as my visualizer. I play Laskey most of the time and the rims are considerably different. MOFWIW, it doesn't matter if the rims are the same as long as you are doing things efficiently.