Raleigh stem
 

I have a '72 Raleigh 3 speed. My stock stem is presently extended as far as it can safely go.
I would like to try a longer stem so I can get in a totally upright position.
Any ideas where I can get a longer than stock stem?

There are a couple of options:

You can get a new stem, such as a Kalloy one, (can't recall the number of the top of my head) and shim your current handlebars or replace them as well.

If you can find the stem and bars from a Raleigh Sprite, that will work, too.

Longer stem is reach and taller refers to stem length. Both are short on Raleigh Sports and not available as stock items on a 3 speed but that shouldn't stop you from swapping out for comfort. Also, maybe a larger frame would be a better fit for you?
Go to any LBS and ask for a used alloy stem that's taller and/or longer as you need it. English North Road style bars are often 25.4 clamp size. If you want real tall the Nitto http://www.velo-orange.com/nitest.html is the the stem you want.

I took the stem from a mid 80s Schwinn World Sport and the bars from a 60s/70s Suburban and put them on my Raleigh Sprite. Works great!

Since these pics were taken, I've gotten a set of Suntour thumb shifters, installed them on the bars and have removed the stem shifters.

http://img708.imageshack.us/img708/5595/23mar10005.jpg

http://img684.imageshack.us/img684/8638/9mar10009.jpg

http://img202.imageshack.us/img202/8702/9mar10015.jpg