Hi Caleb,
Presumably you want to watch the solar eclipse
I'd be tempted to get an A4 sheet of Baader Astro-Solar Safety film for $45 from here:
http://www.aoe.com.au/solarobserving.html
You will have enough material to make a filters for your 80mm, the finder, any binoculars you might have and even to make some eclipse glasses.
I don't hesitate to wrap some around the objective lenses of binoculars/finders with a rubber band for a one-off use during these events.
If you want to reuse your filter(s) make a simple housing with some cardboard and double-sided tape. Just make sure your filter(s) won't fall off! Securing them with tape is a good idea.
I got a 0.5 square meter sheet about five years ago and still have heaps left for these occasional events that involve looking at the Sun.
If you get a filter pre-made for your apeture, it will be more expensive and you wont be able to use the finder, binoculars or your eyes during the event.
Hope this helps.
Have fun,
Doug