From my experience, that sort of restriction is not unusual. You might have some luck with some of the backstreet places on 1-2-1 Da Jie, or the surrounding area. If they cannot help you it will be because that battery type is not, or no longer, available in China.

Good news indeed. Happy for you.

It is still possible to fly directly into Kunming International Airport. A very recent article was linked in another thread on here yesterday. You might find the info in the article very useful.
www.cnn.com/[...]

It depends what you mean by cheese cloth. There is a lot of this type of cloth, which to me is coarser than the cheesecloth back home. It is used for making tofu. I assume that this might be what you have tried, if you have tried in China.

If you have not tried tofu cloth, you will see them sold in most wet markets, in 25-30cm squares. In our market there is a woman who just wanders around on her bicycle and only sells these cloths. They are off white in color.
The problem you will have is that any cloth that is close woven enough to stop finely ground seasonings will be slow. You can speed things up by twisting the cloth until your solids are encased in a ball and keep twisting, or you can grind your seasoning more coarsely.

If you don't like standing around holding the stuff, you can always put the cloth into a sieve, pour in the liquor and walk away, and come back later.

@Janjal. There is a possibility that there are still back street repair shops in Kunming, or one of the suburban villages. If you can find one, at least you and your son could have a mooch around, and see some electronics salvage and repair in action. It would be more informative.

When I lived in the city, there used to be old guys on trikes pedaling around collecting stuff for electrical salvage. They might be a first step on your search to finding a workshop.