I would think that a goo alternator should keep the battery charged good enough for what youre doing. Im assuming that you have a Fleetline Oliver with the side shields? Alot of guys use a mini alternator and it fits and no ones the wiser, thats what were going to do with our 88 when we get it back up and going. I know its not original, but to me function is better than looks. 

Id go with the small alternator and find a small pulley to go on it, even if you have to rev it for a minute after you start it to get it to excite and then idle it back down.