I set off to create a pressurized portafilter to improve the coffee.
1) Cheap espresso machine
2) A rubber cap, such as will fit the bottom of the basket for the espresso machine (I used the cap off a pair of binoculars)
1) Swiss army knife
This can probably be adjusted to fit any low end espresso machine.
Step 1: Trim the cap
Use part of the rubber you remove to create an o-ring to fit at the top of the basket to seal it to the portafilter.
Finally, poke a small hole in the middle of the rubber cap.
Step 2: Test the machine
Note: the o-ring will make the portafilter harder to insert. Be careful not to damage anything, and if you see the portafilter isn't going in at all make the o-ring thinner.
Step 3: Enjoy better espresso