Lactose free. http://www.breyers.com/products/original/lactose-free-vanilla.aspx. Or http://www.Tofutti.Com/.
Alternatives. Sorbet! why not make him a dessert? Here are some recipes: http://bit.Ly/gimj1o. Or give him a bottle of lactaid to take with the dessert. Symptoms of lactose intolerance are often dose related, so a small accent scoop with a rich dessert may be the kindest thing you can do rather than a big dish of ice cream.