For parts, Gun Parts has .32-20 stripped cylinders.
They also have a post-war .32 New police barrel...
Jack First has a new post-war .32 New Police barrel.
I'm just not sure about reworking an old pre-war cylinder to a hot cartridge they were never made for.
Since I'm not sure if this would be safe, you'd need to find someone more knowledgeable about this then me. I didn't do caliber conversion work.
With that said, your biggest problem is going to be finding a usable ejector in .32.
The problem is, first an ejector was fitted to the cylinder at the factory, then the assembly was fitted to a frame by machining the rear of the ejector to set head space.
Then everything else was based off that.
The other factors affected by the cylinder-ejector assembly are....
Cylinder end shake.
Barrel-chamber alignment on all 6 chambers.
Timing on all 6 chambers.
Since all available ejectors are used, they were previously fitted to a different frame and may be too short to fit your frame. There's no practical way to "stretch" an ejector so if you can find one it's pure luck whether you can use it or not.
About all I can suggest is watching ebay and the gun auction sites and hope a .32 PPS ejector shows up and will fit.
About the only way to "stretch" an ejector is to find a Master micro-welding expert and have him weld a bead of steel onto the rear of the ejector, then machine that to set head space.
That would require extensive work to clean the weld up before machining, and you have to really know what you're doing with a small file.
Since I don't know how much you know about the mechanics of the older Colt action, I recommend you buy the Jerry Kuhnhausen Shop Manual Volume One on the Colt DA revolvers.
This was written as a training aid for new pistolsmiths and show all Colt work to Colt factory standards.
This goes into deep detail on such work as fitting new cylinders and ejectors.
This book can save you a lot of trouble and grief.