do a search on toilet flusher, and you maybe able to find some 3gal to 5 gal surge device. Usually the pipe is at least 2.5 inch in diameter to 4 inch.
Try a google search on Carlson Surge Device or Borneman Surge Device. The former is the syphon type and the latter uses the toilet flush valve. Also, you could PM/email Matt Wandell here on RDO, I think he's built a few surge devices...
I have a 65 gallon display with a Borneman surge on top. The Carlson was just too noisy for me. The surge tank doubles as a fuge so it only surges perhaps 4 gallons at a time over 30 seconds. I love it. I used 1" PVC (might be 1-1/4" actually) for the drain and it's a strong surge but nothing too bad.
It's been going constantly for about 5 months now. I've seen it fail a couple times, but that was because the powerhead needed cleaning because the water level wasn't rising fast enough to pull the flapper up (happened after 4 months).
It also failed to fire a few times as well when snails in the fuge were climbing up it and got stuck half on-half off the flapper lip. That problem wouldn't exist if my overflow standpipe weren't so close to the level where the float reaches before pulling up the flapper.
My only complaint are the bubbles, but a cleverly placed powerhead inside the tank can blow them all out of the way.