Just take it shopping with you and try several ones. Needs to be wider than the lamp and at least as tall as base.
If you want to buy something online just make sure you check the measurements first.
Hi Bee: To choose the right lamp shade width, measure your lamp base and multiply by two. For a round base, measure straight across; measure diagonally for a square base. The widest part of your shade should be at least a half-inch wider than the widest part of your base on each side.
Here are a couple of sites that may help:
thank you...I solved the problem...bought a new shade and love the results...now I'd like to decorate