How can I make my TT lights flash unhooked from my truck?

The OP's trailer has a battery, but only the small type that is used on many cargo trailers for the sole purpose of working the electric brakes in the case of a break-a-way. That battery needs to be "upgraded" to a regular RV battery and then add the flasher. This is getting ridiculous. Unfortunately the OP does not seem too mechanically inclined or may not want to deal with electricity issues, but this can't be resolved with one step based on what he appears to have.