が買いたいんだ

want to buy

→ が

phrase Rare #25,122

want to buy が marks what the speaker wants to buy. んだ adds an explanatory or emphatic tone.

JA: 新しい自転車が買いたいんだ。

EN: I want to buy a new bicycle.

お菓子が買いたいんだけど、細かいのがないのよね。

I want to buy some snacks, but I don't have any small change.

地図が買いたいんだ。

I want to buy a map.

トムは革のベルトが買いたいんだ。

Tom wants to buy a leather belt.

新しいパソコンが買いたいんだけど、お金がない。

I want to buy a new computer, but I don't have any money.