I guess you could ask on the day if you can get a ride, but you might find your graded with at least a C or B grade start, due to you not having your grade submitted to the CD grader.
This might seem a bit harsh, but putting a unknown into a lower grade and having them win the race by a long way is not fair to all the other starters in the grade, and as it's a championship event there is the possibility you might not even be allowed to start without having three races with your club.
I have spare club shirts XXL and XL and a vest that I could bring along if anyone is really in need of one, and I am sure some others might also be able to help out if needed.
Also KOCC have some club shirts for sale in the club house, not sure of the sizes however.