Hi #1,
I am not sure what a "frog" is, or at least I am having a hard time picturing it. My dictionary says:

"• an attachment to a belt for holding a sword, bayonet, or similar weapon."

What if instead of a leather belt loop at the top of the sheath/scabbard there was a simple "clip" on the back of the sheath, kinda like the bent kydex clip on the back of my paddle pistol holster, or like the various attachments kydex sheaths use, except not locking. The clip could be used to secure the sheath/scabbard to either a belt or a "frog?" on a baldric. Could the "frog" be a simple piece of leather or sheep skin sewn into a tube that could slide onto the baldric? Maybe the sheath could slide into the frog on the baldric, securing to it with the clip?

Or, maybe the sheath could attach to the frog via a simple leather strap with snap on the back of the sheath? Or maybe the sheath could just have a vertical, instead of the normal horizontal belt loop, attached to the back of the sheath. The baldric could thread through the loop on the back of the sheath, eliminating the need for a "frog".