A macerator pump would work; but as RV Wizard says, if the drain is not at the bottom, you would still have to lift the tank. Not only that, but macerator pumps are expensive (over $200 for the portable pump kit) plus you need a 12 V power source to operate the pump.
There are portable dump tanks with 4 wheels and with the drain on the side that eliminate lifting. Check
THIS LINK for a 25 gal. version - other sizes are available. These have a slide valve similar to what is on the RV drain rather than just a twist-off cap. You just hook up your sewer hose to the outlet and open the valve. You would not need to lift this type of tank. Buying a new dump tank might be cheaper than buying a macerator pump.