Unlike all other languages including English, for almost all Japanese sets UED is harder to find than 1st (except for some of the Decks). Especially The L1 set (HeartGold SoulSilver) and the L2/L3 as well are extremely hard to find in UED.
Here is perhaps a useful thread as well, which contains a list of sets where UED is harder to find then 1st; or where no 1st/UED were released.
Greetz,
Quuador