OTG cable or adapter is the same - well, if depends on the phone's USB type, but that's all - and can be bought from anywhere. You have to be only careful that the cable is data cable.
I've bought mine for about 50 cents from AliExpress some years ago, it's a tiny adapter I have to insert into the USB cable, hence I use it together with Nano S factory cable.
But, while it works with Mycelium, it cannot work with Electrum, simply because that part is not implemented in Electrum for Android.