Slice each tenderloin crosswise into 4 equal pieces. Wrap 1 piece of bacon around the pork and secure with toothpick or wooden skewer. Repeat with the remaining pork and bacon. Sprinkle with pepper. Heat a large cast-iron skillet over moderately-high heat, add the pork and cook until golden brown, turning once, about 6 minutes total. Transfer the skillet to the oven and cook until no longer pink in the middle and the bacon is golden and crispy, 8 to 10 minutes.
In a large skillet over moderate heat, cook the remaining bacon until crispy, 12 to 15 minutes. Remove the bacon and drain on paper towels. Keeping the fat in the pan over moderate heat, add the shallots to the pan and cook until softened, about 5 minutes. Add the demi-glace and wine and bring to a boil, reduce the heat and simmer until slightly thickened, about 15 minutes. Season with salt and pepper.
Serve the pork with generous drizzle of the pinot noir sauce.