Hi Leanne,
Don't stress asking your mother about trying an alternative way to manage your periods; she's a woman too, she knows how it goes! Do a bit of research together on the net (most companies have a website with excellent FAQs), tell her why you want to try a cup, weigh up the pros and cons between cups and tampons. You might be pleasently surprised with how receptive your mum will be!
As for your second question, my personal experience is in the UK, but a chain chemist over here stocks Mooncups in most shops, so I imagine you'll be able to find one easy-ish. You may even be able to have one sent to a store via the internet if that suits you.
Good luck, and hope you're able to get a cup!