Christy, do you want something plug and play, or are you handy enough to do some modification? If you want plug and play, I don't think there is any option besides the Eheim.
Do you have an old Dart laying around? You need a Dart needlewheel impeller and the matching volute, then you can turn it into a needlewheel pump, and on an RS-250 it makes a BEAST of a skimmer. I'm not sure if these parts are even still around. You need to do some modding of the skimmer body too, and it will be external since the Dart can't get wet. Not exactly an energy efficient option (IIRC, it draws about 150-200 watts as a needlewheel pump), and if you don't have a Dart laying around, then it is not a low-cost replacement either. You can also buy the Dart Needlewheel
http://www.championlighting.com/prod...roductid=34380 (that's the only place I've seen them still in stock). It's a long shot, but LMK if you want more info - I remember finding some great pictures around.
Bubble Blaster 5000 I think is another option, not low-cost either - needs some modding. You might find one on a shelf in Canada that pre-dates the exchange rate suckiness though.