I am not sure the Internet has already found out, but some Yaesu radios share the same DC plug size. In my case I discovered that I can power/recharge a VX-8E (VX-8R) handheld with the FT-817 DC cable. The polarity is also the same, with +/positive in the inner contact.
If I wanted to make a spare cable equivalent to Yaesu E-DC-6, the plug size is 4.0x1.7 mm and it is easily available from multiple sources.
I have also noticed that the universal laptop power supply I own, with exchangable heads and several output voltages, has a compatible plug. Althought it might not be an RF-friendly power source, it offers a way to recharge the radio battery. Make sure to set the voltage to 12V