The 46/30 FSA Tempo Adventure crank on the Journeyman uses proprietary chainrings. You presently have no options for smaller rings, larger rings, or other rings.
The small one is an 80mm BCD, which is basically a size FSA made up for this crank. The large one is 110mm but with counterbores on the opposite side from normal, so a standard 110mm ring won't fit.
Going all the way down to 24 once you have a crank where it's possible raises the question of what you'll run for a front derailleur setup. Time was that arbitrarily large tooth count gaps, i.e. 46/24, between small and large on a cyclotouring double were relatively commonplace among enthusiasts, usually on TA or Stronglight touring cranks. In exchange for the wide range, the shifting is clunky. Indexed front shifting doesn't really work with that kind of gap on a double, so no modern systems have it and it's not really seen anymore. If you wanted to go to something like 24/36 on an MTB double, you could do that with an MTB shifter or thumbshifter and double FD with the right specs. There are many questions here that cover the compatibility issues with doing it with your current shifter and/or FD.
If you want to use unorthodox chainring setups and you're staying with flatbar, I highly advise just getting any friction thumbshifter now for your left side and getting used to that. It's cheap, works better than indexed for the most part once you're doing unusual things, and gives you more freedom to do what you want.