13.1lbs. I wouldn't say they are easy to come by or plentiful. I had a set when I first switched to R-comps, but I don't remember how long I looked for them. I remember it being a while and I probably paid too much for them. 
You can get more info about Miata wheels here: http://www.miata.net/faq/wheel_weights.html
The other 15x6 options are heavier, and even harder to come by (aka more expensive).
	
		
			
		
		
	
				
			You can get more info about Miata wheels here: http://www.miata.net/faq/wheel_weights.html
The other 15x6 options are heavier, and even harder to come by (aka more expensive).
	
	
	
	