How can I download Podcast app for iOS5?

My old iPod Touch that has iOS5.1.1 cannot install the latest Podcasts app (as well as loads of others like Gmail, YouTube etc). I found this after restoring the iPod and attempting to re-install the apps I want on it (which is just for listening to music at home; my iPhone5 is mobile with me). iTunes tells me I can't install these apps since the iOS is too old. How can I find the older versions of the Podcasts app for iOS5 that I had until restoring it? Many thanks in advance!