Besides finding additional comps to argue should have been used in the appraisal, is there anything else I should be trying?

Theoretically you could switch to another lender completely and hope another appraiser does give you the value you want, but that's not generally a smart option unless it's the only option (because you don't have the money), because they could come in at the same value/even lower.

You can try finding additional comps, but that rarely if ever works. Imagine if some rando came into your place and work and told you you did something that you do everyday (for money) wrong. "Hey buddy you missed a spot!"

You're unlikely to successfully provide the appraiser with a comp that they should have used, that they're not already aware of. Unless there is a FACTUAL error (the square footage is wrong, the number of bathrooms, the condition of property, etc) you're going to see minimal, if any, change to that report.

If you are so inclined, you can ask your realtor for a credit (obviously not $40K, but something) to take the sting out. That's just dependent on your relationship (or lack thereof) with them.