Your best bet for looking for a specific Pokemon is to use the Family forums instead of the trade shops. It's just 12 Pokemon you want, yes? You don't need a whole thread dedicated to that. Look for the threads containing the Pokemon you want in the 5th gen trade forums and post away!
Oh, here's your list:
"031 Nidoqueen
151 Mew
243 Raikou
251 Celebi
272 Ludicolo
385 Jirachi
386 Deoxys
406 Budew
486 Regigigas
491 Darkrai
492 Shaymin
493 Arceus"