I did a similar BB conversion on a '71 Raleigh
Supercourse using a 5 series spindle scrounged
up at the local Bike Coop. I'm sorry I cannot
give you a source for new ones.

Harris Cyclery used to be pretty good for this
sort of thing:

http://www.sheldonbrown.com/harris/bottombrackets.html

but they now state they are unable to get them.

I'm guessing you want to do this conversion because
you have been traumatized by your cotter encounter.

Look here before you give up on cottered cranks altogether:

http://www.bikeforums.net/showthread...=#post11774914

I am unable to determine your location given
that you have not yet shared it on your personal
page. If you can find a bike coop type place,
they will probably have a stock of salvaged
BB spindles you can try. Otherwise, try to
find crapped out mountain bikes with cup
and cone BB's and cotterless spindles.
They're usually wider.

Phil Wood BB is the nuclear option. Your BB
will then be worth more than the bicycle.

Yours,
Mike Larmer

p.s. I am not a big fan of the rethreading
solution--and I have both the knowledge and
the tools to do it. There are a number of
threads on BF where people say they have
done this and it has worked fine for them.
There are also a few who state it screwed
up their frame. Use the advanced search
function. Also look here:

http://www.bikeforums.net/showthread...ell-ever-tried