Basically, you have three choices...
A Marineland Magnum with a micron cartridge and some powder
A System One
The Magnum and Vortex filters are OK to run continuously, while the System One is rated for four (4) hours followed by a cool-down (30-60 minutes).
As far as charging, I'm not certain how the System One works, but it is a single hang-on-front one-piece solution. Many pet stores use them for weekly polishing, so they must be durable and easy to use.
The Vortex line is probably the old-standby that everybody is familiar with. They are a bit fiddley and temperamental. The newer "DFF" or Diatom Freedom Filter is an updated, improved version of their old recipe. It comes with a "recharge" valve that makes operation much easier. I find mine very difficult to prime and purge all the air from. It makes quite a racket until all the air is out. A purge valve on the cannister lid would be most welcome. Once up and running, it does a great job.
The Magnums come in two flavors: HOB
or under-tank cannister. Not a true diatom filter, but with the addition of some diatom powder to the micron cartridge, you get 95% of the performance and none of the headache.
I've got the Vortex DFF and the recharge valve is basically mandatory. I broke the handle off of mine and decided to replace it with two Supreme Pondmaster diverter valves. It's not as compact or elegant, but it works just as good for about the same money (a bit more by the time you factor in the fittings) and should be more durable.