Consider this, by the time you pay for shipping and insurance both ways, the cost of the replacement sheath, and the wait, you may want to be patient and perhaps another period correct sheath will come up on ebay for around the same total investment of a new replacement. They do show up from time to time. You could also put an add in the buy-sell-trade forum here for a correct period sheath.

The point is, if you spend the time and money to get a new sheath, you are still only going to have the knife, as the new sheath won't add any value or collectibility to your knife.