apartment therapy changing the world, one room at a time

Ooooh, I love cork! Amely, do you have the September issue of Domino? In the article on Jessie Randall's flat there was a picture of a cork lamp in her bedroom. It was very similar to the ones you found except the base on her lamp was more egg-shaped while yours are more rounded. She used a simple slightly-tapered drum shade on her lamp and it looked great.
My suggestion would be to bring one of the lamps with you to Target, IKEA or another store with many sizes of shades readily available. Then you can try out different shapes and sizes. I've been pleasantly surprised with the selection at Linens and Things, the store near me has more shades than those shown on their website. Sometimes it's hard to guess what kind of shade look best without trying it on (at least that's my experience). Write down the dimensions when you find one you like.
Once you are ready to buy, check out Lamps Plus online. Lots of their selection is a bit chintzy looking, but they do have a decent selection of simple drum shades that won't break the bank. They have a cream one with black trim that I'm fond of, it isn't chocolate brown but I bet it would look cool with your lamps. By the way, I love that color yellow on the walls!

I was just at Anthropologie this morning and they have these shades: http://www.anthropologie.com/jump.jsp?itemID=12309&itemType=PRODUCT&iSubCat=413&iMainCat=376 At my location (The Grove in LA) they also have a varity of nice shades at discount plus 40% off.

Coincidentally I was looking for brown shades today too and I ended up with one from Urban Outfitters: http://www.urbanoutfitters.com/shopping/product/detailmain.jsp?itemID=24618&itemType=PRODUCT&iMainCat=336&iSubCat=295&iProductID=24618
It says $22 on the website and did in the store but it rang up for $9, some kind of secret sale! I don't know what your decor is like but those retro bases might look really great with the teal color it comes in too.

I'd use a drum (any height will work with that base, you could go for squat, medium, or very tall) or a flared drum shade. It's a good idea to take one of the lamps with you somewhere like Target or Lamps Plus, just to try out different shades, and find the right dimensions. Then, if you don't find something there, with the dimensions in hand shopping online is very easy. No matter what shade you buy, it can be painted (just need to identify what material you're painting so you buy the proper paint), dyed (easier if it's a natural fiber, try dharmatrading.com for dyes), or recovered with fabric - paper - or wallpaper. So it's quite easy to buy something inexpensive and remake it into what you want. Against the yellow wall, a brown shade coupled with the cork base will tend to cancel each other out (especially in low light) making the chrome and overall silhouette the emphasis, but if you use a colored shade visually your eye will register the lamp better against the yellow wall (hope that makes sense... I've had a lot of trial and error with lamps & lampshades lately).

Check out Moon Shine Shades. They have cool retro styles you can customize. I'm a fan and a customer. Look at their "Porfolio" section for great ideas.

http://www.moonshineshades.com

If you can't find what you're looking for ready-made, take a look at www.lampshadeshop.com. Don't be put off by the strange beaded shade on the home page.
This is a family business that makes reasonably priced custom shades in any size, carries a large variety of fabrics and papers, and will also use materials that you send them.
I have purchased 3 drum shades from them for vintage lamps and been very pleased with the quality, price and customer service.