Murray - do a search - I just ran a quick one and this came up:

"Feline sunscreen protection is trickier Avoid products with Octyl Salicylate, Homosalate and Ethylhexyl Salicylate (common sunscreen ingredients). Products containing Titanium Dioxide as an active ingredient are OK to use on ear tips and noses. This ingredient works by physically blocking the sun's harmful rays, so it is not absorbed (much) by the skin. (This is in contrast to sunblocks that work to chemically block the sun's ray.) The Epi-Pet spokeswoman said that this compound is toxic if ingested, so caution is advised.

Sunscreens contain ingredients that are absorbed through the skin and are regulated by the FDA. All ingredients should be listed on the container. Sun Protection Factor (SPF) has not been rated for animals, and because of this, SPS of animal-specific products should be labeled as "comparable to" their human counterparts, according to FDA requirements."

And from Banfield (here inside of petsmart)- they suggest
"Virbac Pet Guard Gel with Sunscreen (for dogs and cats)"