I have been looking for someone to make a razor that squirts blood as well. But I found this http://www.youtube.com/watch?v=VRm0YiNeGFA
although, that was quite pricey (when I asked for a quote it was way more than I was willing to pay for it). Do you need to razor for the stage production or just to carry around?
And which version of Sweeney Todd do you want to cosplay from?