I happen to own and run my own insurance brokerage so feel I can weigh in here.
Depending on what kind of value or sum insured you require, most good home and contents policies should allow for accidental loss/ damage for "unspecified" personal valuables. Our policies limits are $10,000 per item up to 25% of your contents sum insured. (This is deemed to include Photographic & optical equipment, at least in the policies we provide anyway
) And this shouldn't cost you any extra. It's built in to the wording.
Excesses on most policies are starting from $400-$500 these days so that's something to consider.
There are insurer's who will do this as standalone cover also. I'd be happy to chase up a price for you if your serious about looking into it. PM me with a list of items and individual value and I can look into it. Or we can provide a quote for your home and contents and allow it to be insured within that personal valuables category if your current providers cover is not sufficient.