I've used the Filtron system to make cold brew coffee for a number of years.  I love the way it turns out cold brew.  This piece gets placed at the top of the grounds to help keep them from floating, so they stay in the water and turn into deep, dark coffee.  

But I got tired of buying the guard.  It's not cheap for what it is - Filtron is the only place you can get it as a separate part, so they charge accordingly (plus shipping).  Frankly, they aren't that strong - with a paper filter, you have to try and gently squeeze it in place, and they like to crack in half without much pressure.  If you don't use a paper filter, this probably isn't an issue for you…  but if you've ever accidentally thrown a grounds guard away, this is the part for you :) 

So I thought I would print one.  It's pretty much the same as the Filtron part.  It's not the most complicated design but it should work just fine.  I slimmed it by a few millimeters to try and account for the paper filter, so I wouldn't have to bend it. 

It's a pretty simple print.  I used PLA for it, in theory this won't mess with my coffee.  You'll notice the printed one on the left in the picture, and the original on the right.

I'm sure however you print it, it should not be a tough print.  I printed it at .20 Quality but I'm sure that's overkill.  I'm sure it would work fine at .30 Draft.  For fun, I used Archimedian Chords for top and bottom surfaces.  It is only 1mm thick so you shouldn't need to worry about infill.