I think the odds of your renter's insurance underwriter "bumping" your personal property coverage to include the appraised value of your collection are somewhere between nil and less than that.
I'd suggest finding a broker that deals with Lloyd's of London and one of their peculiar offshoots (there are MANY)- they will literally insure anything for enough premium. You may find that since you will be paying dearly for the coverage, you may not need as detailed an appraisal as you might think-- they don't care if the stuff is worth what you say or not, you are going to pay for $XX of coverage on a pile of stuff, and if that stuff is stolen, burnt up, or destroyed, they are going to pay you ($XX - deductible). Provided you document that you have said stuff, you may need no appraiser. States differ here, too. Even if you need an appraisal, that will be subject to their approval, so step one is finding a company that will write the policy. Then you can make sure your appraisal meets their standards. They will also likely be able to help you find an appraiser, which may or may not be someone you want to use.
Might also check out Chubb Insurance. In any event, my advice would be leave your renter's insurance alone-- it's likely with a major low-cost carrier anyhow like State Farm, Farmers, whatever, and they won't be much help to you for this. Get a hold of a broker that has access to many different insurance companies and who wants to get your business. Be ready to get blown off a lot by lazy brokers who'd rather sell 3 homeowner's policies in the time it will take them to help you with this one thing.
In the end you might find that a good alarm system with smoke detectors and water sensors (yes, there's such a thing) and monitoring is cheaper insurance, albeit not foolproof.
I'd suggest finding a broker that deals with Lloyd's of London and one of their peculiar offshoots (there are MANY)- they will literally insure anything for enough premium. You may find that since you will be paying dearly for the coverage, you may not need as detailed an appraisal as you might think-- they don't care if the stuff is worth what you say or not, you are going to pay for $XX of coverage on a pile of stuff, and if that stuff is stolen, burnt up, or destroyed, they are going to pay you ($XX - deductible). Provided you document that you have said stuff, you may need no appraiser. States differ here, too. Even if you need an appraisal, that will be subject to their approval, so step one is finding a company that will write the policy. Then you can make sure your appraisal meets their standards. They will also likely be able to help you find an appraiser, which may or may not be someone you want to use.
Might also check out Chubb Insurance. In any event, my advice would be leave your renter's insurance alone-- it's likely with a major low-cost carrier anyhow like State Farm, Farmers, whatever, and they won't be much help to you for this. Get a hold of a broker that has access to many different insurance companies and who wants to get your business. Be ready to get blown off a lot by lazy brokers who'd rather sell 3 homeowner's policies in the time it will take them to help you with this one thing.
In the end you might find that a good alarm system with smoke detectors and water sensors (yes, there's such a thing) and monitoring is cheaper insurance, albeit not foolproof.