This page will link to gists containing all the useful seeds I've found thus far for the Item Printer. The seeds are a representation of the time the Item Printer was opened.
These seeds were found by checking every second from 1/1/2000 12:00:00 AM to 12/31/2060 11:59:59 PM. Seeds beyond the limit that can be set on the Switch will take too long.
All times are the exact second that the game uses to generate items. You'll need to calibrate 1-2 seconds before so that clicking "I want to print something!" to start the Item Printer fades to black on the correct second. The format uses 24-hour time.