This post comes froma yahoo group "SecaTwo" that I a member of, and I thought it was a good idea, that would work for any motorcycle.  A database of parts that fit or would work on a bike that they were not specifically made for. Here is the post: 
Hey 
 
I don't know about you people, but I have been having a heck of a time 
finding aftermarket parts for my Seca. I've been doing tons of 
research on my bike (mostly on the internet), and I've started to 
notice that the Seca shares alot of the same parts as bikes like YZF 
600R or FZ-6. On some sites were you can find parts for bikes you 
won't even find the Seca even mentioned even though the part will fit 
your bike. So basically what I'm trying to say is maybe we should 
make a database of all the parts that are compatible with our bike. 
For example; where did the frame for the Seca come from. Could it the 
same frame used the older YZF 600R's used? I have no idea. I'm just 
throwing out ideas. But say it did, then you probably get alot more 
parts for your Seca than you thought you could. Maybe you could 
figure a way to put a better swingarm on and thus get a fatter tire on 
the rear. Anyways heres some of the stuff that I've found out so far 
that the Seca has in common with other Yamaha bikes: 
 
Bar ends: 
 
YZF600R (not R6) 1995-2006 
FZR600 1989-1999 
XJ600 92-96 
FZ1 2001-2006 
 
Pegs: 
 
YAMAHA FZ-1 1000 
YAMAHA FZ-6 
YAMAHA FZR1000 
YAMAHA FZR600 
YAMAHA XJ600 SECA II 
YAMAHA YZF R-1 
YAMAHA YZF R-6 
YAMAHA YZF1000 
YAMAHA YZF600R 
YAMAHA YZF750R 
 
Oil Filler Cap: 
 
YAMAHA (All Models) 
YAMAHA FZ-6 
YAMAHA YZF R-1 
YAMAHA YZF R-6 
YAMAHA YZF600 
YAMAHA YZF750 
 
Gas Cap Base: 
 
XJ600 Seca II 1992-1996 
YZF600R 1995-2006 
R6 1999-2000 (not later years) 
R1 1998-1999 (not later years) 
FJ1200 1986-1995 
 
All of the bike use the same parts. Please help me out and add to 
this. Because I hate using OEM parts. I want to make my bike alittle 
more custom. 
 
Post what you know.