I know many people find them useful but if you are happy with being your own advocate (ie ‘no, you can’t use that arm!’) it may not be necessary. I hate wearing name tags 😊 so I’ve never been a good candidate for tags or ID bracelets! In most cases, not using an arm for injections etc because of lymph node loss is sensible rather than critical - the arm could be used in an emergency for example, probably without any lasting harm. But best to do what makes you most comfortable.
One is deeply tempted to write something short and rude if you do get a bracelet, but maybe not!
Best wishes.