I bought a set from Ground Tech Corp. Planecover.com, Jim Cancil. Phone 800 825-1245. They were custom made and have my N number embroidered on the plug. I don't remember what I paid, I think it was around $40 it was lumped in with a plane cover I bought at the same time. They fit snug in the nose of my 152 and the are tied together with a strap that can be wrapped around the prop, so if you do forget to remove them the turning of the prop will pull them out. Of course that may be the last you ever see of them

I have been very pleased with the cover and the plugs.