Get the preformed type that attaches to a rachet head. 80mm is the size you want and they're about $4 at autozone...

 

I got mine at my local auto parts store.

 

I got a similar one. See attached. Cool thing is that it tightens down on the filter as you twist. The filter has no chance! Mine's 3/8. Just take your replacement filter to the autoparts store so you get the right size.