そう言(い)えばwhich reminds me ..., come to think of it ..., now that you mention it ..., on that subject ..., so, if you say ...

そう言(い)えば君(きみ)の名前(なまえ)って何(なん)だっけ？

Come to think of it, what's your name again?

あ、そう言(い)えばこの前(まえ)のお金(かね)をまだ払(はら)っていませんでした。

Oh, come to think of it, I still haven't paid for the last time.

そう言(い)えばこの間(あいだ)の衣装(いしょう)の事(こと)ですが、あれはコルセットと言(い)うらしいです。

Oh, by the way, about the garment the other day, I heard that it's called a corset.

そう言(い)えばこの記事(きじ)によると国民(こくみん)の政府(せいふ)に対(たい)する支持(しじ)率(りつ)が下(さ)がり続(つづ)けているそうだ。

Speaking of which, according to this article, the public's approval rating for the government continues to decline.

そう言(い)えば、僕(ぼく)のボスが君(きみ)の仕事(しごと)は最(もっと)も出来(でき)が良(よ)いと言(い)っていい程(ほど)素晴(すば)らしいと言(い)っていたよ！

Come to think of it, my boss says your work is so great that it's the best workmanship he's ever seen!