Can you buy these on there own!!

[underground375]

Hi all went out and changed my spark plugs as they have been in the car since 2009, plus I had a little miss fire. Anyway took the old plugs out then but the new plugs in. Noticed the plugs ends are pretty much crumbling away. Not good.

So put it back together anyway and now im running lumpy half the time on 2 cylinders. Can you buy these am there own?