There's one option that could cover both the uses mentioned in the OP, but it's not all that "cheap"
 
Savage Model 24:
Rifle top barrel, shotgun lower barrel
 
 
http://www.gunsinternational.com/Savage-Combination-Guns.cfm?cat_id=574
	
		
			
		
		
	
				
			Savage Model 24:
Rifle top barrel, shotgun lower barrel
http://www.gunsinternational.com/Savage-Combination-Guns.cfm?cat_id=574
	
	