Continental european pilsnermalt should do it. That's at least what many breweries which makes kolsh use..
I see often in Kolsch-recipes that there's some wheat to them. I just read an article by a homebrewer who traveled to germany to seek out Kolsch. He spoke to several brewers /breweries in the Cologne-area. Most of the grists were just 100% pilsner malt. Another proof that the europen classic styles are about process, not ingredients.