How would you draw the lewis resonance structure for CH2Br?
There are no resonance structures. There is only one valid Lewis structure for the bromomethyl radical.
The Bromomethyl radical has only one possible Lewis structure. This molecule as written in the question has an odd number of electrons
Resonance structures are multiple valid Lewis structures for a molecule that differ only in the electron placement and serve to delocalize charges. Since this radical has no charge, no double bonds, and bromine is not the central atom, there are no resonance structures; only one Lewis structure is valid.