You can get an oil dispencer/pump from the parts store that should work. I've once used an empty gear oil squeeze bottle and switched to an antique oil pump can since then. But do your Getrag a favor and buy an extra quart and over-fill the transmission. Fill your 4 quarts that you already have in the normal fill hole, then plug it. Then take the very top bolt out of the PTO cover, then use your oil pump with a small enough spout to stick in the bolt hole, and pump in the extra quart. Your Getrag bearings will not run dry with addition of the extra quart, which is a design flaw that becomes apparent when towing with the normal oil level of 4 quarts. I've even added 8 oz of an antifriction additive called Energy Release, which really quieted down the transmission in addition to making it run cooler. Feel free to PM me if you have any questions.
Mike