Here it is, an exact one block piston replica that pushes exactly one block! It runs on 240 Hz!
It uses a little thyme script to spawn water to simulate piston extension.
Best of all, you can move it anywhere you want, and it's not glued to background!
Left is 4 meter version, which works best, but inaccurate (1 block ≠ 4 meter), and resource-intensive due to huge amount of water.
right is 1 meter version, which works not so good, but accurate (1 block = 1 meter), and less resource-intensive due to less amount of water.
Unfortunately, redstone (or electricity) doesn't work here, so it extends by default. However, you may retract it manually by erasing all the water.
Want to put this thing into your uploaded scene? Even a tiny credits would be nice!
Have fun pushing things around!

Don't forget to comment and rate (by going to the standard browser and copy-paste the URL)!