Bottle feeding

I've been breastfeeding for 5 months, but have tickets to go to a concert in 3 weeks and a show at end of Dec and am hoping to get him feeding on bottle. Have been pumping and trying but not working yet. I have tomme tippee bottles that 1st baby used. Just brought a NUK bottle to try. Not sure what else to try- just hard and annoying that I pump, warm it up and the have to tip it away when he doesn't drink it.