+1 on what DonT said.
I had to replace all the pots in my Prophet 5, and I found some at digikey that were the same size, but I had to do ALOT of modding to get them to work. All the originals were frozen or broken due to long storage, neglect, and anvil case foam deterioration/moisture.
WCS lists pots for the Pro One, but says email for options. They will probably be pricey.
Also, check with Doug at synthparts.com. He may be of help.
I have no idea if the pots of the P5 are similar to those in the Pro One, but the digikey part # for 100k is 450D104-6-ND (theses pots are solder lug type, not PCB mount). My machine was a basket case and then some. But the replacements worked out great and only cost $75 and some time (WCS would have been about $400 for the pots alone).
I can post the writeup here if anyone is interested.
