#1
The cord I have that runs from my 5150 pedal (the distortion/crunch/effects switcher thing) is defective.

Does anyone know of where I can get a cord like that?

It's like a long cord at the ends it has male prongs, ermm 7 prongs in a semi circle to be exact.
#2
sounds like an XLR to me (might be wrong) but they should be quite common
#3
It's not an XLR. Contact Peavey maybe they can send you one? Or maybe your Peavey dealer can order one for you?
Peavey 3120
Mesa 2x12 Rectifier Cabinet
Jackson RR5
Jackson DKMG
LTD EC-1000
TC Electronic Polytune
BOSS RV-5
BOSS DD-7
MXR 10-band EQ
EHX Small Clone
Dunlop 535Q Crybaby
BOSS NS-2
Voodoo Lab Pedal Power 2+
#5
You might have to special order it through a peavey dealer (I think Long and McQuade is... I'm not sure as I havnt been to one in awhile), cause its not easy to get a 7 din pin cable, especially one thats like 20-30 feet.

Online may be the least trouble some way to get one. This one should work:
http://www.samash.com/webapp/wcs/stores/servlet/product_7%20Pin%20MIDI%20Cable%2030%20Foot_-1_10052_10002_-49978024?cm_mmc=Froogle-_-MIDI%20Cables-_-7%20Pin%20MIDI%20Cable%2030%20Foot-_-RM7CABLE

And to the others:

Its not XLR at all, as he said it has 7 pins on each side. Its basically like a midi cable with an extra 2 pins that transfer power for LEDs on the footswitch.
Reinhardt 18 Head
H&K Tubemiester 18 head
Blue 6505+ head

TC Electronics G Major
MXR phase 90, Pigtronix Echolution 2
Digitech Whammy (5th gen)

ETB Infinity x2
ETB Yoda

Frust