One More to add
The replacement diaphram for a Stromberg Carb. on 68-69 Triumphs (I think) are almost perfect replacements for stock diaphrams. Almost perfect because they are slightly beefier and will alter your throttle response. If you keep your ride in perfect tune and are ultra-sensitive (or a racer) you will notice a difference.
Moss Motors in Riverside, CA and the Web has the parts for about $15/pair.
I will have to do some more research for the part number.