I've had a policy for a long time through my membership in the NPPA. It's an inland marine type deal that covers total replacement both on-site and on location, from anything really barring conflicts and usual insurance stuff like unforeseen acts of nature and crap like that. There's an additional rider--cost about 50 bucks extra--that would cover not keeping your gear in a locked trunk. Basically, you need to keep your stuff in a locked vehicle, or be able to prove the theft from a police report. They tried to offer an incentive though, to keeping your stuff in a locked trunk. I've never done that since I drive station wagons & trucks....
The nice thing about the policy is that it covers your gear if you drop it or anything that happens to break it on the job. If for instance, you dropped a lens and had to send it out for repair--it would cover this and would pick up the tab for the rental of another if you needed it. It would also cover all rental equipment under the policy as well. You have a month of grace period to add equipment, so if you buy something and haven't added it yet, it will be covered automatically for up to a month.
You can insure anything--cameras, lighting, darkroom stuff, computers, even negatives and slides. Anything you listed, and declared a replacement value for--is covered, but there were a few clauses. One, is that the minimum deductible is 500 dollars. The minium costs for coverage are on several tiers, with the cheapest being about 500+ dollars a year covering a min. of about 10 thousand dollars worth of gear. So, you have to sort of itemize your equipment out to meet these schedules. When you run over the limits, then they start pricing out by the hundreds of dollars--and then things started incrementally adding up.
What I would do for replacement cost, was to look at Shutterbug (this was back in the late 80s, early 90s when I first got into this policy) and canvas the local camera stores and come up with an average price for replacement for the gear in question. It usually took a few weeks to figure this out, because I always had a mix of old & new equipment. In some cases, I opted for what it would cost for a brand new item. In others, I just decided what it would cost for me to get some similar used item.
I started covering basically everything, and then over time it just got too expensive and I realized that covering "classic" cameras was a waste of money because I was using Nikons and more modern cameras on these jobs. Replacement costs for these classic cameras is sky high and just impractical on a working type policy. I might use a Leica for maybe 10% of my freelance work and the rest is done on Nikons or Mamiyas. I just wound up facing the fact that if my M4 gets ripped off, I'm s.o.l. Life goes on. I started thinking of these older cameras as play cameras, and taking a hard look at what I actually used in my freelance work. That's when my policy became more realistic and streamlined. So-- I quit covering little things and just went for bodies and lenses and power packs and heads. Quit covering grip equipment, stands etc. Just the stuff that I need to work with. Everytime I buy a new piece of gear, it's a shuffle with booting off old stuff to keep me under the minimums. It's not just "can I afford this lens?" but more like "can I afford to insure it?".
So my advice would be to inventory your stuff--all serial numbers etc and then itemize into work and play groups. Look at what you've done over the past several years and think about the stuff that would hurt you the most if you lost it. For me, there was alot of sentimental attachment. But the actual work cameras, I never used for anything but that. It's really almost impossible to place a dollar figure on a sentimental attachment to a camera....pretty easy to come with one if it's for your business though.
Hope this helps.
KT