They are on Chambers' website.
https://www.flintlocks.com/parts.htmDepending on how much room there is between the vertical posts, it might be possible to braze a bar onto the side of the front trigger.
The front trigger bar is mostly there to help you when you want to let the cock back down from full cock to half cock or rest positions. It gives you a convenient way to lift the sear while you are moving the cock. A lot of people have written that it gives you the option of firing with the front trigger, and technically, it does. But I'd think that to be very, very rare. My point is to say that the front trigger bar normally doesn't take much punching.
Tak, Chambers also sells a Davis double set trigger on the same webpage. It's a double bar trigger. It might fit just fine, if you change out the entire assembly. Would have to use the whole thing. Might need to trim down the front of the Davis trigger plate a little.