Here is a post from Analog Mike's Vintage Guitar Effects Forum.

More info on Speed pedals coming soon, but for now read this. There are some good suggestions of what to get.

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Info on pedals:
Here's the deal - you can use just about any pedal that has a pot in it.
Some will work better than others. In the best cases, the speed change will
be nice an even throughout the travel of the pedal. In the worst cases, the
majority of speed increase will happen in the last 30% of the pedal's
travel. But in just about all cases, the speed range will be as good as, or
better than that of original Univibes and the many clones that offer pedal
control of speed. The low impedance keyboard volume expression pedals give
the best results.

Proel PVP16L. Does a great job of controlling speed, and it already has a
wire coming out of it that you can plug right into CC2. Also, it's cheap -
only $30.00! Jay gave a link in his post. Most of the mail order chains
carry it. http://www.zzounds.com/love.music?p=p.PRLPVP16L&z=1196192099324

Boss FV-50L Stereo Volume Pedal. Also does a great job, it's stereo, so you
only use one side. This one has in and out jacks, so you need a Send/Return
cable. That's a cable that has a stereo 1/4" at one end, and breaks out to a
pair of mono 1/4". You can find that at any music store, usually under the
"HOSA" brand name. This pedal is a little pricey - around $80.00

Boss EV-5 Expression pedal. This one has a cable coming out that plugs right
into CC2. I've had mixed results with it. I have one that works like a
charm, but I took a CC2 to a music store to try out pedals, and when I tried
their EV-5, it wasn't so great. There's an adjustment on the side that seems
to help. It's around $60.00

Rogue VP-201 Stereo Volume Pedal. You can get that at Musician's Friend.
It's a stereo volume pedal, but it should do the job quite well and it's
only $20.00. You need to get a Send/return cable with it. I never tried this
one, but it looks like a good candidate.

Ernie Ball - I have their stereo volume pedal. It's built like a tank - the
quality is incredible. But it didn't work so well as a speed pedal. It did
the job, but too much of the speed happens as you press the pedal all the
way down. I think this could be improved by adjusting the gear in the pedal,
but I didn't want to mess up the whole string mechanism. These are up around
$80.00

Not Recommended: Active volume pedals like the Dunlop High-Gain, any of the
Morley pedals. They won't work.

Here's a link to a Hosa "Send/Return" cable, the type you would need for
hooking a standard volume pedal up to a CC2 for speed control:
http://americanmusical.com/item.asp?UID=2001103017554884&qty=1&item=hosstp202

Want to have some fun? Take your CC2 to a music store and ask to check out
expression pedals. I've taken CC and CC2's into Guitar Center a couple times
and it never fails to draw a crowd. People will want to know where you got
it, the store manager will want to check it out, other people will want to
play with it.

I hope this helps!

Dave