こんなんじゃ一生みつからないでしゅ。sounds like anime Japanese, and it is normally, こんなんじゃ一生みつからないです。Or こんなことでは一生見つから無いです。 It won't be found forever like this/with this pace. もう! is taken as a shorter form of "本当に
The usage of this いいかげん is somewhat peculiar. But Japanese people may use this いいかげん in daily conversation. This いいかげん has similar nuance of "もういいかげんにうんざり can't stand anymore" The speaker really wants to buy new clothe (probabl