I would just keep looking. Number 10s seem to be in short supply locally, but I've had no issue getting number 11 caps. Try Scheels and Cabella's. Both of them have caps in stock locally. Eventually they'll be back on the shelves and listed online again. Just don't pay those price gougers if you can possibly resist. You aren't going to need to go fight a civil war with percussions guns.... well, hopefully you won't,
so just be patient and next time, stock up so you won't be caught in short supply the next time this happens.