For sour you could use Citric Acid also known as Sour Salt, or Lemon Pepper or such things that are sour. For bitter you could use Coriander, Chocolate, or even Coffee. Umami can be done with either Accent (MSG) or other things like Worcestershire powder, powdered mushrooms, or even some seaweed flakes (look for most powdery) or Bonito flakes.
You can always Google "Bitter Spices" to give you more leads, and do that for each thing you are looking for.
If there was just a handful of ways to get there, we wouldn't have so many different rubs out there. So just find a methodology, and stick with it until you like what you have. THEN if you like you can change your methodology completely to make a rub to compete against the first one you liked, and so forth.
Have fun! I know I did.