Difficult subject indeed.
I have not found exactly what you are looking for, but searching a bit I found some Fengtien armbands of earlier periods.
This template shows two Fengtien armbands during the mid-20s. In the Osprey book from where it comes, they say the red on white armband was only one of many used by Fengtien. It seems Warlord armies used a lot of different models. Usually they had a white circle in the middle with the Chinese character of the Army or the superior officer of the unit, like here (Machinegunner 00:00):
Also early Nationalist Army (and Communist and the Ankuochun) used red armbands.
I hope this help you a bit.
PS: I found no way to resize the picture. Sorry.