AR-15 is no problem. You can buy one that was made before a certain date in 1993 or you can buy a current one as long as it's a "post ban" model. Stag Arms is a good choice and they are located locally in New Britain. Go to Hoffmans or any other dealerand you have lot's of choices. You will not be able to buy one witha folding/collapsible stock, bayonet lug, suppressor, or grenade launcher though.
As far as AK-47 as long as it was also made before a certain date in 1993 and it's only capable of firing in semi automatic mode you should be all set otherwise forget it.