If it is a recent production double, you might have to try and buy one from the maker, or alternatively have one made, or make one yourself.
If it's a vintage double, make one yourself or get one made.

Even if you could find a tool for a 3 hole bushing, there is no guarantee that the spacing, shape, or diameter of the pins would be correct for your rifle.

Bushings in some guns can be installed really tight, and need a tool which fits precisely, or the bushing can be damaged.

In my experience firing pin or striker breakage is not all that common in field use.
I believe a high percentage of striker breakage in DR's is a result of damage caused by dry firing, or constantly firing on poorly made snap caps.

3 Pin Tool
Disc Set Strikers