Sarah, the bags are Tourmaster slant 2 models - size large I think. I've had them for quite a while so check the Tourmaster web site for current models.
The K & Q seat doesn't give you any real back support as such, just a bit wider and softer.
Triumph OEM products are quite expensive so be prepared for some sticker shock - but it's quality stuff and looks great.
I would ride the bike for a while before you make a decision about the mirrors.
I bought my Bonneville in December 2005 and it sat at the dealer all winter until I picked it up in April. We get serious winter weather up here.
Once a month I would "visit" the bike over the winter and had the dealer install an accessory to spread out the financial pain
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