The function complete for you
DELIMITER $$
CREATE FUNCTION `FIND_IN_SET_X`(inputList TEXT,targetList TEXT) RETURNS INT(11)
DETERMINISTIC
BEGIN
DECLARE limitCount INT DEFAULT 0 ;
DECLARE counter INT DEFAULT 0 ;
DECLARE res INT DEFAULT 0 ;
DECLARE temp TEXT ;
SET limitCount = 1 + LENGTH(inputList) - LENGTH(REPLACE(inputList, ',', '')) ;
simple_loop :
LOOP
SET counter = counter + 1 ;
SET temp = SUBSTRING_INDEX(SUBSTRING_INDEX(inputList, ',', counter),',',- 1) ;
SET res = FIND_IN_SET(temp, targetList) ;
IF res > 0
THEN LEAVE simple_loop ;
END IF ;
IF counter = limitCount
THEN LEAVE simple_loop ;
END IF ;
END LOOP simple_loop ;
RETURN res ;
END$$
DELIMITER ;