Untapped perhaps, because it might not be feasible.
- What size are these letters ??
- How many fluorescent colors do you need ??
- What degree of intricacy will be needed ??
- How many [letters] are needed all total ??
For a screen printer to flood fluorescent inks and then cut it out, this sounds expensive, especially it there's only gonna be a few.
Why don't you just buy the fluorescent vinyl, apply it and then cut it out yourself ?? Keep all the profit in-house.