Rather than make something specifically for the Funkey, I looked at existing containers and cases that would be the right size. The Funkey is 42.5 x 44.5 x 13.8 mm I found this leather earphone case (60x50x25mm): https://www.amazon.co.uk/dp/B07PMCDVTD/?coliid=I1BI13H82XC4O2&colid=F9PWAXPFCJP6&psc=1&ref_=lv_ov_lig_dp_it And this metal tin (70x70x23): https://www.aliexpress.com/item/4000077615204.html?spm=a2g0o.productlist.0.0.95e37d021Fdh2a&algo_pvid=55867758-978b-4c81-a462-f6737c52bda0&algo_expid=55867758-978b-4c81-a462-f6737c52bda0-10&btsid=0b0a0ae215955930596075139e7e84&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ The tin has enough room to add foam padding to really ensure it stays safe. Feel free to share anything else like this below.
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maybe A54 here (50x50x18mm): https://www.aliexpress.com/item/32859689704.html?spm=a2g0s.9042311.0.0.2edf4c4dLuaKRy
The leather case looks good. Douglas Barros apparently found the same on AliExpress : https://www.aliexpress.com/item/32906960345.html
Currently cheaper from this seller :
https://www.aliexpress.com/item/4000430402825.html
The A54 plastic box is a great find, but it has rounded corners, so we need a try to be sure that the Funkey S fits in.
I ordered the A54 plastic box, and now that I am holding it, I think it is very good.
Sure, it is just a cheap box made of polypropylene, but the build quality (fit and finish) is better than I expected. The inside is smooth, the lid closes very well, and I do not see any defect.
As for the size, a 43x45mm rectangle easily fits inside, despite the box corners being rounded and despite some locking tabs taking up 3mm of inner space. There is even room for some foam padding.
As a cheap and easy solution for protecting and carrying the Funkey S, I think it can do the job.