There are one or two I know of. Personally I use Photoguard
but this may not be the best for you - the details of coverage vary, so check carefully. For example, Photoguard has one rate for amauteur/semi-professional and another for professional. Some companies don't allow for semi-pro use. I also wanted the public liability cover provided.
Check too for the costs if you plan on taking your equipment outside the UK.
You are right to consider the risks of carrying that much gear around, esp. since Myrtle Ave. and other LHR
locations are well known photo spots (and not just by the good guys!).
Colin K. Work, Pixstel