I've used a place in Apopka for years to cut sandblast masks - They are a pretty good sign shop called Vital Signs. 407-297-0680 A bit of a drive for you from Brooksville though.
But for probably about the cost of having vinyl lettering cut & installed, you could get one of those photo films like cchardt has on his truck back window. One of those would work GREAT on that trailer! However, I don't know the name of that sign shop he used.
Did you get that trailer? My future sis-in-law said you asked about the one she had for sale. Congrats if you did. That's a pretty nice trailer.
matt.