Every grocery store I've went to has never heard of it. I would also like to know where to get it. So here is a bump.
Sorbitol can be purchased online, but I do not use it, so I searched using the phrase
retail sorbitol
There were several links.
I worked for a friend who sold baked goods, including diabetic baked goods, that she brought here from New York City. I can tell you that Sorbitol is one of the artificial sweeteners used by companies that make diabetic chocolate, and that eating diabetic chocolate can cause severe lower gastric problems, gas, cramping, "the runs".
Unless your father specifically wants or needs you to use Sorbitol, I would suggest you try another type of sweetener.
Theresa 
Cheryl -
Check with your server to see if they have groups available. I know there is a diabetic recipes group on Yahoo.
Splenda, Equal, and Sweet'n'Low all have recipe sections. The Splenda recipes I know, for fact, are all TNT recipes. I have not read that the other two companies have tested their recipes before posting on their website, but I am sure they did. They would be foolish not to.'
By the way, I absolutely hate artificial sweeteners - there is not a single one that I cannot detect in food and drinks. But I have had the Splenda version of Apple Pie. It was refrigerated before serving, and the cold made it very very difficult to detect.
Theresa
health food stores should carry it have to watch how much you eat works like a laxitive.
Sugar alcohols like sorbitol can be laxating in used to excess, but, they're one of the only ingredients that provide sugary texture in sugar free desserts. In cake, this translates into moistness and volume.
Splenda only provides sweetness. Unless you use 50% sugar splenda for baking, which is 50% sugar, which, imo, is unsuitable for diabetics.
Cheryl, if you Dad's been a diabetic for any period of time, I'm sure he's familiar with sugar alcohols. There all over the place in commercial sugar free candies and ice cream (because of the texture they provide). Just ask him what sugar free candies he eats and how he tolerates them. If he says "I can't eat that stuff it gives me the runs," start looking into other options. There's an excellent chance, though, that he'll say something like "oh, I love that stuff, I can eat it till the cows come home." If he says that, make your way to a health food store, get your hands on some sorbitol and bake him a cake.
Quote by @%username% on %date%
%body%