Iruka is obtainable via spending coupons at Treasure of Sage, i forgot how much is he but not more than a thousand coupons so its affordable .. And for the part of "better ninja that gives similar buffs" then some ninjas gives same buffs like iruka but not exact and the thing there is, what the ninja buffs ..

At 30%,he cost 840 coupons,and you can get him for free by refine ninja frags.You need 5 star ninja to refine its fragments,so may be a little slow to get him this way.