I am gathering parts for the Armstrong in my other thread. Track and MLBS have little, everything that is close is out of stock. The Gun Works in Oregon does not list anything useful. The trigger guard is very small. The nose cap will be for a very slim barrel. The pipes are small. I do not find small scale parts listed anywhere.
Who else supplies pistol parts?
I can't help you with the trigger guard, but why not make your own pipes and nose cap? It's not as hard as it looks, and will get you what you want and it is quite satisfying.
I make my own nose caps, and just made three pipes today. This is not to brag at all, it's simply to say that it can be done by the idiot typing now, and it results in what you want without having to wait for shipping. And it is satisfying.
I'd be happy to explain how I do it, and I'm sure there are tutorials as well. My way may not be the best way. Feel free to PM me.
Cheers,
Norm