If it's a frog pond and you don't have fish and aren't feeding the pond, you don't need a filter. Just have lots of plants and they will keep the water clean.
If you want a filter on the pond, either get an external power point fitted by an electrician, or run an extension cord from the house to the pond. However, this can be risky if people mow the lawn so it is safer to have an electrician do the job properly, or put the extension cord in some orange conduit and either bury it it put it on a frame overhead so it can't be damaged.
You can also use an air pump to run an air operated sponge filter or undergravel filter in the pond. The air pump sits on the back porch or somewhere out of the elements. You run some airline from the pump to the pond. The advantage of airline is if it gets damaged, the only thing coming out of the hose is air, so there is no chance of being zapped like you get from a cut power cord.