Any of the Bakeries (Petit is excellent as MikeR said), La Rotisserie or Mayas to Go, most of the restaurants and all of the private chefs can do this with a little notice.
yeah a word on cake excellence in St Barts...my wife is the granddaughter of a woman who did most of the special occasion cakes for most of northern Vermont....she handed her down her skills and her pans etc to Wendi who is also pretty damn good at it......and Wendi tells me that the cakes and pies she has had the pleasure of eating in St Barts take a back seat to no one ....
You can find lots of restaurant numbers here Restaurant List
Most of them are even correct , but I do need to do an update. There are a couple of restaurants that I missed, a few that have closed, and a few new ones.