Speaking from experience, take your time! Your event is far enough away that you have many options, that need not cost an arm and a leg!

Another option, would be to purchase a used tuxedo tails coat, and have it made into a PC. There are many sites that sell ex-rental wear for very little money! Several members have done this with good results.

If the formal jacket will only be used a very few times, why spend a bunch of money?