I have found that having a keychain with a small stuffed tiger on it has been well accepted. It hangs on my side all day, and the only response I have gotten out of it has either been positive, or none at all. I think people find something like a key chain to be one of those places that you store random things that you pick up, that don't necessarily mean anything. What they don't know, is that it is connected to my undying love of having stuffed animals.
I now am getting a new wallet Amazon.com: Stephen Joseph Tiger Wallet: Toys & Games with a tiger on it. I suspect i'll get the same response, either a positive teasing and jealousy, or just no response.
Are there any other objects that you can think of that are common, that can probably be more childish without completely exposing your little side? Aside from t-shirts, which are pretty bold to make childish looking.