On Thu, 12 Jul 2012 22:49:29 -0700 (PDT), wrote:

Like you'll find in my 2nd post/follow-up, I did measure it
and they were pretty large, I'm not sure if anybody still
makes rectangular LEDs as large.

They don't. I don't have a Commodore 1571 handy to dissect, but as
others have suggested, it's not a packaged LED, but rather a block of
plastic with an LED inserted into a hole in back.

My goal is to put such large LEDs as HDD activity indicators on my PCs and external hard drives.

I presume that there's some reason the indicator needs to be so large.
Personally, I find the flashing lights to be somewhat of a
distraction, especially at night. The blue LED's are the worst. I
have partly covered the blue LED's on my Dell Opti 960 and DirecTV DVR
to prevent being blinded at night. If I turn off the room lights,
both LED's would be bright enough to read by in the dark.

I've had some minor experience with illuminating blocks of plastic in
the 1970's. I was helping design a radio, that included a molded
plastic front panel strip with imbedded T-1 3/4 LEDs. The initial
design looked awful. The lighting was horribly uneven and not very
bright because of color mismatch. Eventually, the mechanical designer
(not me) had to sit down and calculate the light distribution and
exact color of the plastic, in order to produce a usable product. I
suspect you may need to go through the same process with your plastic
block. For example, the block may be large enough that two LED's are
required. Polished sides of the block look very different from
diffused (sanded) sides.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558