Info about Chinese Embroidered Kaidangku (split crotch baby pants)

I found these in a a huge junk shop in brooklyn, and cannot find ANY similar pieces online to compare them to. I know they are called Kaidangku, and that they are traditional Chinese baby/toddler alternative to diapers. I've seen several photos on Google, and tried every combo of search terms to find a pair of similar style so I can determine what they are worth and how old they are. I know we are not allowed to ask for each other's opinion on pricing/value, but perhaps somebody is able to point me in the direction of somebody/somewhere that I can find that info.

They are cotton feeling, with light padding between the 2 layers. The bib has 2 thin straps, one of which is detached on the front. There is some simple machine straight stitching as well as hand stitching with thicker thread. The hand embroidered dragons on each leg are vibrant and in great conditon.

Thanks in advance for any tips or info!