Heat broiler. Coat broiler-pan rack with nonstick cooking spray. Soak twenty 6-inch bamboo skewers in warm water for 20 minutes. Combine maple syrup and barbecue sauce. Set aside.
Cut bacon in half crosswise. In batches, cook bacon in skillet over medium heat about 3 minutes per side lightly cooked but still flexible. Transfer to paper-towel lined-plate; let stand until cool enough to handle. Cut onion into wedges; separate pieces. Place 20 pieces on a plate; microwave on HIGH for 30 seconds.
Cut chicken into 20 pieces, about 1 inch each. Wrap cooked bacon piece around chicken. Thread 1 slice onion onto skewer, then bacon-wrapped chicken, then pineapple chunk. Repeat, filling all skewers. Divide maple-bbq sauce in half. Brush skewers with half the sauce.
Broil skewers 4 inches from heat for 4 minutes; remove from oven and turn over. Brush with remaining sauce. Broil 4 more minutes. Serve warm.
Note: For ease of preparation, buy peeled pineapple slices in the produce section and cut into 1-inch chunks. Skewers can be cooked several hours in advance; cover in plastic wrap and refrigerate. To serve, heat in microwave until warmed.