Past, Present Future
This online retailer out of Minneapolis has an incredibly huge collection of mid-century furniture, as well as what appear to be some new pieces crafted in a solid vintage style and made to your specifications. Tanker desks, club chairs, sofas, book shelves, and even clocks and staplers.
For a few hundred bucks, you can have these vintage pieces restored in a basic manner. For double your money you can secure a custom restoration job, with a huge assortment of powder coat finishes, fabrics and linoleum choices (depending on what item you are having redone). Also, if you are planning on making your own wanna-be period televisions series of Mad Men, you can talk to them about prop rental furniture for your sets. If I lived anywhere even remotely close to Minneapolis, I'd be in their showroom browsing around instead of writing a blog about tables I can't afford!
Oh, and the other thing I love about Past Present Future's site is that they happen to have a ton of images from old product catalogs for some of these pieces. You know I love me some vintage product ads. For more, check out their "tables" section, and look at the bottom two rows of thumbnails.
Etsy
I hardly EVER go to Etsy. Don't ask me why. I even have a store (with nothing in it, apparently!) and still hardly bother to wade through the masses of handmade craft projects and overpriced vintage clothing. BUT I somehow was directed over there while Google searching "tanker desk" and lo and behold...people sell furniture there!
Ebay
I know many people have had success buying vintage cars and parts on Ebay, and I assume buying some huge vintage office desk would be about the same. Of course, as always, shipping these things is a bitch, so you are best off searching in your particular area and picking it up yourself. I didn't have much luck, but since I'm always wasting time browsing that dame site, I might as well continue to keep my eyes peeled.
Craigslist
You know...there's always this.