Sapporo is not rice beer. Rice beer = sake. Sapporo is, like Kirin, a light world-wide lager beer. That means it has malt in it, as well as a relatively high proportion of adjunct - probably rice. But not more than 50% rice.
If you're an experienced all-grain brewer with lagering capability, you mightbe able to brew a beer like Sapporo. But it'll be easier for you to brew what you like and for him to continue buying Sapporo. If you're up for the challenge, go for it - you can even make a decent example with extract only - but you must have the ability to ferment it cold.
Bob