Increasing milk supply

Is it possible to increase milk supply when my son is 8 months old? He gets so frustrated nursing during the day and I'm assuming my supply is low considering I work (as a server at a busy restaurant) three days/week and I work for 8+ hours straight without time to pump. So I just bought a little manual pump on Amazon because it got good reviews and I freaking hate my electric pump because once I sit to pump, I'm stuck for like 25 minutes and can't get up to do anything. I'm just feeling like a manual pump might make everything easier to pump.

Anyway, can I still increase my supply this late in the game? And any tips??