Are they something one can just order online and swap on to the Python without any fitting or difficulty?
I had $3000 saved for a stainless 6" Python... but apparently those are prices for the black rubber grips. Factory wood with Colt Medallions are about another $300-$400.

Yes you can order aftermarket wood grips, Old OEM take off's can be found but they will be PRICY. Yes, well made one's will fit fine, cheapo's, well, you'll get what you pay for.

Darn... was hoping someone made quality aftermarket grips that were as good as the OEMs... and had Colt Medallions.

There are A couple companies that make them with Colt Medallions, Eagle Grips makes some nice ones but as I said, you'll pay for quality ones.

Seems like $240 for really nice looking factory appearance grips with medallions.
If Eagle Grips are really nice quality, I'll just keep a lookout for the best condition/priced 6" Stainless Python then regardless of grip!

There are several good substitutes available with Colt or Colt replica medallions.

One source are the "sort of" copies of Colt factory grips sold on Ebay. These are usually made in Asia from fancy hardwoods. Some of the medallions looks like Colt, until you look close and see they're are nothing like Colt medallions. Others have close copies of genuine Colt medallions.

A very good source of Colt type grips are made by Altamont. These are made of laminated woods. Altamont made the last Colt wood Python grips for the late 1990's Python Elite. These have finger grooves.
Altamont makes these for several other sellers which other options, including checkering patterns and with laser etched designs:

http://www.altamontco.com/pistol-grips/colt/python/

http://www.gungripsupply.com/viewcategory.php?groupid=24

http://www.handgungrips.com/Python_Custom_Grips/2057/c/3077