Hello,
I lurk here mostly for tips on holster making as that is my primary leather interest, but your post caught my eye because I too would like to make a leather jacket and have had zero luck in finding a good pattern. Since your post has gotten zero replies in almost a month, I figure this is as good a place as any to submit my 1st post.
One idea that I have come across (I forget where), is to look for a very inexpensive jacket (at Goodwill, flea market, etc) that is of the general design that you want to copy-emulate, and then carefully cut & disassemble that jacket in order to use it as your pattern. The article wouldn't necessarily even have to be made of leather.
My ideal motorcycle jacket would be something on the lines of a Fox Creek Commander, or perhaps a "Classic"...
http://www.foxcreekl...nsjackets.phtml
...with a gun pocket, & with articulated & hardened internal leather armor ( ie, couir boulli) built in to the jacket. Something like a compact & minimalist version of this type of stuff ...
http://leatherworker...showtopic=18945
http://leatherworker...showtopic=16175
..instead of the plastic Forcefield armor that Fox Creek uses.
Anyway, I'm currently looking for an extremely cheap "Classic" type motorcycle jacket that I can dissect in order to create my dream jacket. Thought I'd share.
Take care and good luck,
OR