SNX token does not appear on list of tradable tokens on the zapper exchange on both ethereum and optimism.
It should show up as it is available on the matcha front end.
Edit: Inconsistent behavior from user to user. Some have access to it only on Ethereum, some have access on both, neither in my case.
Same issue for synths, some have access to all of them on Optimism, in my case only sUSD shows up on the list (see screenshot).