My older brother built a parts washer years ago,used an old stainless steel kitchen sink,a 35 gallon drum,and for the pump he bought a cheap marine bilge pump,that had 3/4" hose barb fittings..found it at a discount store for less than $25..
At first he had fears the pump might not like solvents,but he filled the washer with Safe-T-Clean commercial solvent and he used it many years with no signs of the pump failing..
That said,I thought Harbor Freight sells just the pumps separately ?..maybe one of those will fit yours,or can be adapted.