Hi Steve / Terry
I would suggest you go for the tennis ball idear, my Delta did the same thing ,
i try'd the fish tank pump and found it wasn't powerful enough, tried the tennis ball worked better but kept on moving out from under the arm ,
ended up with a cube shape, squeaky dogs ball, took the squeak out and fitted the blower pipe in the hole
--- hey presto !------ were back to work again , better than the original !!,
been using it 3 years or more now.
-------Frank---------