Hi!
It's always hard when a student's timeline does not line up with a teacher's timeline. I assume you have already spoken to your teacher regarding your position... Does he know that you are planning on retiring from dancing next year? If not, he might be willing to squeeze in one last comp for you.
If he can't do this, perhaps you can ask him for a recommendation for another teacher that can take you to a competition in his stead. You can video tape your current routines and have your temporary teacher learn them, if they are willing to do that.
Not all teachers are okay with doing a one time competition with a student, but some are. Just be sure to be clear with the new teacher about your intentions so that there are no uncomfortable misunderstandings.
I'll write again if I can come up with a better solution for you. In the meantime, good luck! Let us know how it goes!