Hi Nicole,
What speed film are you using? because as far as I can remember FLD and FLW filter have a fairly large filter factor, about one and a half or two stops which would effect your ability to hand hold the camera, or you might need a faster film. After reading your question I had a look at Cokin filters they make a FLD filter for mixed lighting which could fit your bill, it,s an A139, and probably wouldn't be half as expensive as a glass one, afterall it's not something you use every day.