I too struggled with the same problem. I have tried the K-Kaps with varying success as they also tend to leak.
Below is what I now do. It sounds like a lot, but it really takes very little time. I read once that K-Cup coffee costs about $50 a pound if you figured it out. Yikes!! Not sure about that, but I'm a single dad with two kids in University and I really needed to trim a bit off of my budget. This was an area that could help.
What has worked best for me, is re-using the plastic K-Cups. After brewing, remove the K-Cup, let it cool, peel off the foil, then rinse it out and dry throughly.
When I want a coffee, I just grab one of my used, dry K-Cups add my favourite coffee. I cut a bunch of small foil squares ahead of time and I simple re-seal the K-Cup with a new foil top, crimping the foil highly around the edges. I have NEVER had a leak, it works wonderfully.
Some argue that this defeats the convenience factor of the Keurig machine and I can't disagree, it does add a little extra work. At the end of the day, I needed to save a little money and re-using each K-cup 4 or 5 times really saves money. If I am pushed for time, I use a new K-Cup, but most days, I use a used one.