Let's talk outfits.
How about the gym lesson? Here's Bella's gym outfit.

http://www.amazon.com/Simple-Womens-Retire-Slip-Black/dp/B000WBEPOE/ref=cm_cr_pr_product_top
http://www.amazon.co.uk/JERZEES-NuBlend-Sweatpants-True-Red/dp/B004Y1CYBE/ref=sr_1_15?ie=UTF8&qid=1334440597&sr=8-15
http://store.americanapparel.co.uk/2102.html?cid=199
And finally, here's Bella's 'Goody Stay Put Grip Headband' (which she wears CONSTANTLY throughout all films. Sorry, I can only find it on ebay, so you'll probably have to look for it yourself but if you're lucky enough to catch these two lots, here's your headbands!
http://www.ebay.co.uk/itm/FREE-SHIP-2-Goody-BLACK-Stay-Put-HeadBands-Bella-twilight-Head-Band-/260992586964?pt=US_Hair_Accessories&hash=item3cc45ed4d4#ht_721wt_1078
http://www.ebay.co.uk/itm/FREE-SHIP-4-Goody-BLACK-Stay-Put-HeadBands-Bella-2-Pks-Head-Bands-HTF-NWT-/261001796451?pt=US_Hair_Accessories&hash=item3cc4eb5b63#
Off to prom~
The dress: http://www.amazon.co.uk/Blue-Banana-Cobalt-Halter-Dress/dp/B002KM9B5Q/ref=sr_1_9?ie=UTF8&qid=1334492041&sr=8-9
Cardi: ebay - I can't seem to find a replica, so I recommend just buying an off-white cardi, some beads and flowers and get creative!
Shoes: Converse! (and one of those cast things)
Will you marry me?
Here's our lovely couple! >:)
Bella's Wedding shoes, VERY EXPENSIVE! :o $1295.00, apparently £817 :O (£816.931617)
That, my friend, is a rip off. It's more expensive than the wedding dress!
But they're beautiful
American again, sorry! But it's only £14 so grab it while it's on sale c:
VOILA!