How to increase the carry load of backpack?

You don’t as sad as it is to say you can find a larger backpack exploring as a rare item or simply spend real life money on a backpack. If you going to spend money for backpack wait for days on end.. Different offers pop up randomly and you get the chance to buy a large backpack for real cheap. I came across an extra large backpack with 15 extra spaces 200 gold coin and some kind of gun for $10 flat. In the store I can’t find that backpack for half as cheap.. In the store I’m looking at $30+ for the same backpack and less gold. Keep an eye out for offers that’s where you get lucky.