do you have a cat burgler?

I'm definitely not an expert on this, but have a 6 year old human kid, with whom I do rubber stamping from time to time. We use non-toxic ink pads that we buy for about a buck at Walmart, and the ink from those washes off very quickly and cleanly- at least from human skin and rubber stamps. The nice thing about those also (probably true of most rubber stamp pads nowadays) is that the pad is raised above the case it is in, so you can tap it against a hand, paw, rubber stamp, etc. very easily (re: quick and with complete coverage).

Anyway, they come in a lot of colors, and I would think they would be safe, especially if you wash his little paw right after.

I just got rid of some old office type ink pads that were from about 20 years ago. I'd be much more wary of using the older, more stain prone ink- the ones that don't list as non-toxic.