www.car-parts.com will give you a good idea. I believe you are talking about a 3800 SC engine with supercharger. Most places sell them separate. I would say they go for $800 and up. Here is a cut and past from your area.
1995
Engine
Pontiac Bonneville 170K MSS42517 $1100 GreenLeaf OH Massillon USA-OH(Massillon) E-mail 1-800-843-1010
1995
Engine
Buick Riviera 8-94,FWD,MFI,3800,AT N3279 $900 Pierce Auto Parts USA-OH(New-Paris) E-mail 1-800-762-2951
1995
Engine
Buick Riviera NEEDS TESTED IN DISMANTLE,NOISEY 138K C0430J $850 J and J Auto Wrecking USA-OH(Marshallville) E-mail 1-800-425-1555
1995
Engine
Buick Riviera GOOD RUNNER LESS CHARGER 051604019 $600 Cleveland Auto Wrecking USA-OH(Youngstown) E-mail 1-800-362-2773
1995
Engine
Buick Riviera -charger, good mileage BU0001 $600 Voll Auto Parts USA-OH(Toledo) E-mail 1-419-476-8921
1995
Engine
Buick Riviera CORE 2A1111 $Call Sass Automotive & Wrecking USA-OH(Cleveland) E-mail 1-877-311-7277
