Ok. I see what you are saying... I tried to zoom in to see the model number of the existing pump, but couldn't.
Judging from the comments, on that page, if it takes 3/4 inch plumbing, you can just replace the adjuster with a 3/4 inch gate valve. Other than that, look up the model number of the powerhead, and just order one a little larger (700-770 gph will give you about a 50% increase) if you decide to keep this skimmer. Just make sure that all of the parts will interchange so the new one will fit the existing parts. Shouldn't be that hard of a find. Just looks like a small mag pump from what I can see on the pictures. Make sure you don't get a powerhead too strong and overpower your skimmer body. If you have it with you, you can post the numbers on the existing pump, and hopefully google will tell us what we are dealing with up front...
I haven't heard much about that particular skimmer, so it's a little challenging to shoot off some advice, but, I hope I've helped...