Ive just got one of these! I just went to one of the main stations and asked and they gave them to me there. As I look very young (22 but look about 16!) I find people give me really dirty looks when Im on a bus and Im not the first person to offer my seat to the elderly, so Im hoping the badge might help that.
But also Im 23 weeks pregnant and Ive barely got a bump so I just look a bit podgy and unless I told people (or were to wear a badge!) people wouldnt be any the wiser, so instead of me being grumpy about them not offering their seat Im just making them aware, and then I can be grumpy if they dont offer their seat! It can be a little embarressing wearing it (theyre bigger than I thought lol) but I just pin it to my bag