Stainless Steel Bottles seem to look good nowadays, used on the Tour a long time ago and now, I don't know why, seem to have made a comeback. Maybe because they are more sanitary and definitely, durable and can be cleaned.
Plastic is a flimsy product. I had an older Peugeot bottle that came with the bike but it got vertical cracks.
I'd venture, for a real '70s look, you want one that has the little shower thing on top, the salt shaker top along with the drinking top. Much like this:
http://cgi.ebay.com/REG-Italian-White-W ... 286.c0.m14
In fact, the Peugeot one was like this one I think, no stamping of the brand name on their, just a white bottle.