I'm 100% on your side on this, so please don't take this the wrong way...
I am starting to become convinced you aren't going to do anything about this, and never were going to. Your true hope is just to scare him into getting this back to you quicker than it would otherwise take, and with the work completed by him so the cue stays original. That is your real goal here. I mean maybe you would actually do something at some point some day who knows how many months down the road, but you never had any intention of doing anything until now (they were always empty threats), and you don't have any intention any time soon either.
You have been telling him "if I don't get my cue back soon..." every two weeks for months and months now, and it means about as much as when he has been telling you "i will get it done and shipped to you in two weeks" over and over for months and months now. This thread was a hollow threat. Everything has been hollow threats. It reminds me of a mother that always tells her kid "if you don't stop doing that I'm going to spank you" yet she has never followed through and actually spanked the child even once in her life and her kid knows it and therefore the words are meaningless and have no effect on the kid and the kid just continues to do whatever they want because of it.
Some months back you said you wanted your cue back immediately in whatever condition it was in and no further work was authorized and nothing less was acceptable but as soon as he said he would do the work and get it to you in a few weeks you couldn't say ok fast enough. The same thing happened when you started this thread, "I want my cue back immediately with no further work done to it and nothing less is acceptable..." but as soon as he said give me another two weeks the answer of course was "ok". Even in your post above you are once again saying ok to the 37th deadline extension request from him. If you really wanted your cue back even if it was incomplete you would have told her to just take it to the post office tomorrow. I have no doubt you will continue to threaten action, and I also have no doubt that as soon as he says he will really get it done this time in the next week you will again acquiesce and the cycle will repeat just like it has been for however many more months it takes until he finally does actually finish your cue and get it back to you whenever he finally feels like it.
Others have said essentially the same thing I'm saying in a more round about way, that you are being weak with the repeated empty threats over a long period of time. More important than others seeing it is that John sees it and knows they are hollow threats too so it isn't motivating him in the least to get it done any faster than whenever he feels like getting around to it. Keep telling him every two weeks "I better get my cue back in the next two weeks..." because it means nothing to him and makes no difference because you never do anything but say the same thing again in two weeks. Again, I don't intend any offense and I am fully on your side, but at this point it is time to either take action (it was time many many months ago), or it is time to stop complaining and just sit back and wait and you will get it when you get it (because waiting to get it when you get it seems like what you are going to do anyway). Sorry this sounds harsh but time for action was a long time ago and you are in a way very complicit in this too if you really think about it because you have been an enabler by giving in continuously over such a long period of time. Trust me when I tell you he takes you less serious now than he did months ago because now you have a proven record for just giving in every time. Act, or sit back and wait however long it takes. Those are really the only two choices.