declare @db_list table (dbname sysname)
declare @dbname sysname, @query varchar(8000)

insert @db_list(dbname)
  select name from sys.databases
  where name not in ('tempdb', 'master', 'msdb', 'model')  -- feel free to change as needed
  order by name asc

while (select count(*) from @db_list) > 0   -- one way to iterate, the list is small enough that this will have no impact
begin
  select top 1 @dbname = dbname from @db_list
  select @query = 'use ' + quotename(@dbname) + '; INSERT THE NEW SP_SPACEUSED SCRIPT HERE'
  exec(@query)
  delete from @db_list where dbname = @dbname
end