Well, I would imagine that any equipment bought with "business" funds would not be covered if there was a break in. At least that's what I was told when I asked did my policy cover a home office.
It's a ridiculous situation which just allows your current insurer to squeeze some extra cash out of you. I'm in the same position. I work from home with just a laptop and no visitors to my home, but because i bought the laptop with my 'business mastercard' it's not covered.
As said already, I'd say there are plenty of policies out there that will cover it. Or you could just try putting the pressure on your current insurer?