You might consider using the cloth room to fit the top to the figure. It may be possible to export the item as .obj, then load it back into Poser and save it as a prop. Once made into a prop, if it is not "double sided" you should be able to  bring it into the cloth room with the figure, clothify it and get it to fit that way. I'd say it's worth an experiment to try it.

It's all fun and games...
Until the flying monkeys attack!!!