Actually it’s probably not fine on the '817ND.
https://groups.io/g/ft817/message/112816
TLDR: You should put a 4k7 or 2k2 R inside the powerpole adaptor or the radio may flatten the internal battery when off.
btw, to answer the original question, I looked at the pile of left over right angle plug on jacks that come with generic wall warts and found one the right size and used that with a bit of hacking the black plastic off.