Took a 390s on trade and it didn’t have the transport screw. No response from ML so I started trying different thread sizes. It’s a 10/32. Purchased a 10/32 x 2" machine screw from Ace ($.19) and ended up cutting it to 1 1/2" and tapering the tip with a file so it catches the transport threads. Opened up the unit just to be sure and the transport was solid. Hope this helps someone else looking in the future.
NOTE: This may not be the same for the # 37
NOTE: This may not be the same for the # 37