Replacement buttrest question.

I did the buttrest to backrest mod, but sometimes I ride 2 up with my girlfriend as a passenger. She cannot sit comfortably with the backrest in place so I end up leaving it at home and riding with nothing. This gives me a backache on an all day ride, so I'd like to pick up a spare buttrest and all the bracketry to quickly swap them between buttrest and backrest without having to wrench the backrest all apart returning it to stock.  They appear to only be a little over $40 if I am looking at the right thing in the parts diagram. My question is the diagram points to the buttrest and gives the corresponding number 12, but when you look at the parts list below to get a price you get two different part #'s and prices for 12.  First, what do the two different numbers represent, and second,  do the buttrests come complete with both the brackets installed on it making it a seamless swap??? It doesn't show athe brackets as a stand alone part that I can see. Anybody have experience in ordering this?  Link to parts diagram and price list I am referring to. >>> http://www.ronayers.com/SEAT-C198013.aspx

Really?!?!  There is no one that has bought a back-up buttrest to swap or just replaced a bad one? Guess I'll just have to take my chance and order one of them and hope I guessed right, and that it is complete.

som2002,
I have a Honda Silverwing Parts Catalog that I purchased from Helm a few months ago.
It lists the backrest as part number 77210-MCT-640. it also shows the brackets attached.
It is also item # 9 in this official parts list. Item # 12 is the seat catch (latch).
The parts list from the  http://www.ronayers.com/SEAT-C198013.aspx is not quite the same as the Honda Printed Parts Catalog (14MGFA01) dated 2012.
Hope this helps.
Rich

I forgot to mention that my Parts catalog is for 2010, 2011, 2012 FSC600A
and 2010 FSC600D Models. There may be a difference in prior model years, I don't know.

Well, I haven't... But my seat is still as it came

Thanks Rich, since that part # you gave me is one of the two listed for 12 at RonAyers, and the cheaper of the two choices  , I think that will be a safe bet to order it then. Thanks again for your help.