Don't know of any Dwarf Colombians.
Corn Islands are rare, that's why they're expensive. I don't know why they sell pairs only, but it's probably got something do to with them not wanting to sell 1 male and 2 females to people and then get stuck with 3-4 males at the end of the season.
Vin Russo sells his Hogs for around 250 shipped and they are pure as pure can get. Crosses are around 125-150 shipped, try pmherps.com for those. Paul does that Sunset thing over there.