打着灯笼也难找。(Dǎzhe dēnglóng yě nán zhǎo.)It is not to be found even with a lantern; It is hard to come by.

Explanation

“打”是“提着”的意思。“打着灯笼也难找”是一句俗语，意思是在光线很好的情况下也不容易找到，比喻很难得，不容易得到，通常用于劝诫人。可以用作定语等。
“打”(dǎ) means “carry or hold”. “打着灯笼也难找”（ dǎzhe dēnglóng yě nán zhǎo） is a proverb which means it is hard to find something even with a bright light. It is a metaphor for something difficult to get. This proverb is usually to exhort somebody. It can be used as attributives.
Words:

义务yìwù:voluntarily;
机会jīhuì:opportunit.

Sentences

1、Jiă:Tīngshuō tā yǐjīng yìwù zhàogù zhè ge lǎorén èrshí duō nián le.
甲：听说她已经义务照顾这个老人20多年了。
A: I heard that she has taken care of the old man voluntarily for nearly 20 years.

Yǐ: Tā zhēn shì dǎzhe dēnglóng yě nán zhǎo de hǎorén a！
乙：她真是打着灯笼也难找的好人啊。
B: It is rare to find such a kind-hearted woman.

2、Jiă: Wǒ hái méiyǒu juédìng yào búyào qù cānjiā kǒuyǔ jìngsài.
甲：我还没有决定要不要去参加口语竞赛。
A: I have not decided whether to enter the oral contest or not.

Yǐ: Yídìng yào qù, zhèyàng de jīhuì,dǎzhe dēnglóng yě nán zhǎo a!
乙：一定要去，这样的机会，打着灯笼也难找啊！
B: You should go because it is an opportunity which is hard to get.