Bought the Ugreen Silicone Case for Apple AirPods  from Lazada  for S$4.15 during Lazada mid-year festival sale. The usual retail price is S$5.19. Shipping to Singapore is free on their Saver delivery option where it will take 13 to 16 days to reach you.
As the name of the product suggests, the case is made from silicone, and there are three colors to choose from, red, black, and dark blue. I picked black.
It comes with a carabiner so you can hook it on your bag.
The case measures 53 x 46 x 24 mm and the silicone is 1.6 mm in thickness.
There is a cover for the lightning connector port and an emboss over the setup button position.
The only downside is if you are using your AirPods with a Wireless Charging Case, the charging indicator in front of the case will be blocked.