The name of the Keurig accessory is "My KCup", and it comes in 3 pieces - the cone, the bayonet-connect cap and a mesh filter (lioiks like a tiny version of the wire mesh filters in the big models).
If you like your coffee strong, over time you just have to experiment and come to know how much coffee to add to the mesh filter and you will no longer need the KCups again. My preference is for one slightly rounded teaspoon of Fine Grind.
I don't like mine bitter or sharp, so I drilled a 1/2 inch hole in the bottom of the mesh filter (it's plastic, not wire) and use it just to hold a paper filter in place. I started with the Number 1 size (pre-formed, not a circle), but they are getting kind of expensive (and rare) so I tried the number 2 filters (also pre-formed) and they work just fine - even the cheap yellow-label no-name ones.
I start by folding the bottom up about 1/2 inch, then the top across enough for the basket to fit, then the other end over that. Open the filter top and space it out with your finger, push the basket in, then push basket and filter together into the cone. Add your coffee, then the cap, and make a brew.
I find the paper filter gives me the strong rounded flavour like I get in the store, but with the mesh alone it's too harsh for me.
I hear tell that for a true cup of Timmy's you should put a few drops of maple syrup in the bottom of the cup before you brew... works for me!!
BTW, I looked at all the other devices on the market for making your own coffee in a Keurig - don't waste your time and money. The My KCup is very sturdy and works just fine.