You could always wear them

If you are getting on the train at a station without controlled access to the platform, (i.e. not NYP, 30th street...) then you might have a better chance. Linger in the background a bit when the train arrives, and just choose a door that is not manned by a conductor or have an "associate" ask the nearest conductor a question to divert attention and then dash on the train.

Personally, I'd go for it.

If the train isn't crowded, they should lay flat in the over head rack, and may not even be noticed. Of course if it's a packed train, then you may be sunk. If you have a particular train in mind, see how expensive last minute tickets are going for. If they are still relatively cheap, then that may not be a typically crowded train (e.g. I know if a same day Regional fare from NWK to PHL is $45.00 or $64.00 then it is most likely not a full train).