I recently found that O'Neill makes a slickskin wetsuit jacket called the O'rginal Beaver Tail. It looks almost vintage perfect except for the snaps. It is much closer to "period correct" that Spiros' jackets or Vintage Soul. You can get different colors on the side panels, but all black is available. Sizes run from Small to 3XL. Online prices are between $95 and $115. The only downside is it 2mm thick. I haven't decided to buy one becaues of the thickness (actually thinness). If so, I'll post a review.
Here's some links, but I have no connection to either place:
http://www.thaliasurf.com/oneillbeavertail.html
http://www.hansensurf.com/Oneill-Mens-W ... acket.html