Perhaps you should ask your tour company (and/or travel agent, if you used one) whether there is an insurance company they would recommend. Although you may not be able to find something cycling-specific, you ought to be able to find companies that provide policies covering participation in non-professional sports. You should be able to specify individual high-value items on any travel insurance policy - there will be a limit per item and for the total value of specified items, but it should be a few thousand dollars.

Hope that's vaguely helpful.