Brian,
If you are a member of the NSRA I would advise you to take advantage of the insurance they provide. I made a claim last year on behalf of our club to replace an Anschutz thumbhole stock which had suffered a similar problem to yours (ours split across the grain, adjacent to the slot for the bolt, but was equally unrepairable). I found the process straight forward and quick. Having got a letter from a gunsmith verifying that the old stock was not repairable, we purchaced a new replacement and forwarded the receipt to the insurance company who then reimbursed us minus the excess on the policy.
James