Is it feasible to finish the bachelors at somewhere that would provide you with that? I'm thinking about schools that have a great reputation in the field that also have undergraduate programs with crossover options for the undergrads to take classes with the grad students (so you could shoot for doing all the construction coursework with the grads), like NC School of the Arts and Boston University?

Even at our school, where there is not a specific concentration for undergrads in costume production, those with the gumption and dedication to seek it out can get some great experience and coursework by working in our shop and taking some of the grad classes for UG credit. I always have at least one undergrad or continuing ed student in my crafts classes, and the graduate intro to draping and beginning pattern drafting courses often have as many undergrads as grads in them.