There's abit of info here and some good looking DIY Consoles too!
It looks like you'd be best to create something to your liking in cardboard first to trial fit etc and then using this as a pattern for a wood or ally unit that can be trimmed to match your interior as required.
Moss do a ready made Armrest...
Hope this helps.
Many thanks for the reply pretty much what i thought about doing your own template,but was hoping there was a few templates out there to get some rough dimensions, might be a project for the dark nights of winter