Interestingly, the most deeply personal thing anyone usually has is their own name. If you can’t get a physical object for energy connection, get the other’s middle name(s) instead, and write them on the candle. Use the whole name when you speak the ritual words.
Alternatively, if you know the person really well, childhood friend, happened to see right through them, whatever, you can use an epithet to grab onto their innermost being. I did this once without a name, but saying “boy.” I knew who he was, but his innermost being was immature and insecure, so i hooked him with “boy” because it was always so close to the surface of his consciousness.