You could do something like this:

USE tempdb;

DECLARE @source_table varchar(100)='sys.all_columns',--Source Table

@dest_table varchar(100)='new_table',--destination table (created by SELECT INTO)

@column varchar(100)='is_column_set',--column to swich to NOT NULL

@sql_prep varchar(1000),

@insert_sql varchar(1000),

@alter_sql varchar(1000),

@data_type varchar(100);

SET @sql_prep='IF OBJECT_ID('''+DB_NAME()+'..'+@dest_table+''')'+' IS NOT NULL DROP TABLE '+@dest_table;

EXEC(@sql_prep);

SET @insert_sql='SELECT * INTO '+@dest_table+' FROM '+@source_table;

EXEC(@insert_sql);

SELECT @data_type=DATA_TYPE+

CASE

WHEN CHARACTER_MAXIMUM_LENGTH IS NULL THEN ''

ELSE '('+CAST(CHARACTER_MAXIMUM_LENGTH AS varchar(5))+')'

END

FROM INFORMATION_SCHEMA.COLUMNS

WHERE TABLE_NAME=@dest_table

AND COLUMN_NAME=@column;

SET @alter_sql='ALTER TABLE '+@dest_table+' ALTER COLUMN '+@column+' '+@data_type+' NOT NULL'

EXEC(@alter_sql);

You would supply the values for @source_table, @dest_table & @column. Obviously this script, as is, will only work for one column but you could easily update it to handle more.