Its a $13 part. Get it, then it is a 20 min job to try it for fit on the action. The hardest thing is getting the sear spring tensioned while trying to insert the pin. If you take your action out the stock, you will see that there is just a single pin holding the sear in place. Hardly complicated. Awkward regarding the spring, yes.

You could try the action in your new stock and leave off the trigger guard temporarily, then see if you can push down the sear from above with a screwdriver or pin punch to remove the bolt. If you seldom need to remove the bolt from the action in the field, and you can depress the sear lever with a tool from above, then you could simply cut off the extension that savage added to the bottom of the sear for the trigger guard release. That way it would fit in any Savage stock made for a side release. This may get you in the game while you wait for a replacement sear of the correct type.