On our cement pitch I've used a 3rd hand part roll of artificial grass that I got from the local cricket club. It was a bit short, so I bought a couple rolls of cheap artificial lawn from a hardware shop. If you are using light paceman balls, the artificial lawn is probably thick enough to even out most of the iregularities, but this might not be the case with heavier balls.
The cement pitch played perfectly, but did wear out the seams on cricket balls.
The 3rd hand artificial pitch is good on the balls, but has some creases and wear that give you a few surprises.
The artificial lawn plays nice and flat (if you get the joins right), but you do get some green stain on cricket balls from friction, but not a problem with light paceman balls.
If you go to any carpet shop, they are always replacing and throwing out perfectly good carpets that would suit your needs. Asking there would be a cheap place to start.