You can try fenugreek, it made a massive difference to me. Also pumping after every feed, even if nothing comes out. Pump, break a few min, pump again - simulate a GS
I don’t get much pumping now either. With DD1 I started pumping from the start and end up with a massive oversupply. Could get 100ml in one sitting easy. Now I’ve only pumped a bit and I only get 50ml in one sitting. I don’t do it regularly though. If you want to pump to be able to give a bottle you should find a time you can do it regularly and stick to it so you start producing at that time.
Keep in mind that some babies will Take a bottle even if full.
Anyway, I swear by fenugreek and pumpathons 😜