Hi Tangerine!
Here's a link to the "Adorable Apple" post Angie made. I think reading this will give you a few ideas about what to look for when shopping for clothing.
http://youlookfab.com/2006/05/.....ble-apple/
Now, as far as suiting goes--what is this suit for? I think you maybe could wear a pencil skirt, but you might need to experiment with how fitted and tapered it is. Two things about the jacket though--it needs to button below the bustline (have a low stance), and it needs to be nipped in at the waist. A boxy silhouette will only emphasize your tummy area.
I think you're going to have a difficult time finding a suit that is available in any sort of bright color (and I'm not sure you'd want to because it wouldn't be very versatile). But you can make a suit more playful and colorful by wearing it with an interesting blouse. J. Crew and Banana Republic both carry suiting in size 16 (but only online, not in stores). Both of the stores make a great quality suit, too.
http://www.jcrew.com/AST/Brows.....uiting.jsp
http://www.bananarepublic.com/.....o?cid=5013
J. Crew's suiting line is more traditional, but they offer a lot of fun blouses that would look great worn with it (and on their own with jeans, too!). You want to maintain that V neckline, I think that would be most flattering on your body type, so I'd recommend something maybe along these lines:
http://www.jcrew.com/AST/Brows...../95001.jsp
http://www.jcrew.com/AST/Brows...../93675.jsp
http://www.jcrew.com/AST/Brows...../91377.jsp
And as far as BR, these blouses would be great:
http://www.bananarepublic.com/.....pid=587884
http://www.bananarepublic.com/.....=587899002
http://www.bananarepublic.com/.....pid=592123
Of course you should experiment and see how each thing works on you. Also, I'm definitely no suit expert (I think Sihaya might be), so hopefully others will chime in and make some suggestions as well.