Photo sponges for wiping 4 x 5 negs

I am currently 'studying' with one of the great masters , now 83. He has suggested that I purchase two large viscous sponges for film. I cannot locate them anywhere? Anyone know of a source? I use LFN or Photo Flo but I have occassional water spots and am trying to eliminate that issue.

I haven't used sponges in many years. It could be a difference in water sources, I know. I use a spray bottle with rinse aid (LFN and Ilford's - I'm out of Photo Flo) and haven't had an issue with water spots since. After spraying, I take a look at the film with a bright light in the background, and spray a little more on suspicious areas. You may want to try that before taking a chance on scratching your negatives with a sponge or squeegee.