If a kiltmaker in the US could do it in that amount of time I would advise to get it here. Depending on where he stopped in Scotland there is no guarantee the kilmaker could get it to him in that short of a turn around. Also, 500 pounds for a kilt is probably about 875 dollars and that does not include the 17.5% vat.
Alexis Malcolm may be able to do it if she is not backed up. I followed her measuring instructions for my kilt and it fit perfectly when I got it. Her prices start around $385 for a traditional kilt and she will work with you to try and meet your deadline.
As for a tartan recommendation, I would recommend the U.S. Navy Edzell tartan. It is generally accepted as official tartan for the Navy. If he doesn't want to go to the expense of the Prince Charlie jacket right away, he can wear his Navy Mess Dress jacket with the kilt as it has the same cut as a Prince Charlie and the Navy tartan kilt is usually authorized for wear with the Mess Dress Jacket at official black tie functions such as the Navy Day Ball, so he will get some extra wear time for the kilt.
He already has acceptable shoes, so the only other expense will be for hose and a fly plaid if he wants one, belt (since you normally don't wear a vest with the Mess Dress jacket), buckle, and sporran.