Way outside my comfort zone

I work as a bid writer for a small charity, with the odd bit of community fundraising thrown in. We've had an amazing offer from a grant-making organisation to go along to their fundraising golf day at a very swanky club in the summer, to talk about our charity as an example of one which has received a grant.
The issue is that I am tall, so off the peg clothes don't fit, I'm over 60 so need something to cover up, the dinner is black tie with a James Bond theme and I'm generally found in jeans and sweater! This is so totally outside my experience in terms of fashion and social circle.
With all the troubles the world is facing, this ranks as a very trivial issue but I'd welcome any thoughts.
Miss Moneypenny, perhaps, or even M except that I need to come across as open and friendly.