I have an old Southern gun that has been animalized by a century and a half of gunsmithing morons. But, all the screw ups on this old warrior aren't bad. They are like a roadmap into the thinking of the time. The solution for the same problem you have is pretty simple. The old timer built a staple that spanned the ramrod channel, yet still fit into the forward inlet. This was engaged by a hook, attached to the forward extension of the trigger guard. The rear extension was held with a single screw. Installation was pretty straight forward. Just, slide the forward extension in until the hook engages the staple, and then spring the guard down into the rear inlet and secure it with the screw.
Hungry Horse