We built ours from materials we had around the house: Some pieces of wood left over from other projects and a sponge padding form an outdoor cushion that we no longer used (I too off the fabric cover and washed it). The only thing we bought was a small piece of new vinyl tablecloth that my husband stapled over the padding. And this is the result:
It is so much easier on my back to change my baby here. And I can reach everything without going away from the changing top. My diaper stacker with cloth diapers is hanging on the left side from the crib and the dresser with her clothes is right behind me when I change her. If I need to leave for some reason, I can just put her down into the crib - very convenient.
The changing top lies securely over the crib and can not move because of these two pieces of wood which are holding it in place from both sides. Yet it can be taken down when baby is sleeping in the crib.
And here she is - my sweet 7 month old cutie pie on her new changing table.