What do you do when your pump schedule is thrown off at work?

I'm a FTM and have been back at work for about a month now. My baby is 4 months old and EBF, we nurse at home and I pump at work to send bottles to daycare. So far I have not really had a problem pumping every 2-3 hours at work; I have pretty much been able to adjust either my pumping schedule or my meetings to make sure I never have to go longer than 3 hours between pumps.

Next week, I have a 4 hour long meeting. It's not at my office, and the drive isn't long enough for my to pump in the car so I will have to pump before I leave. Meeting ends at 5, so I will leave straight from the meeting to daycare pickup, meaning I will likely go about 5 hours without pumping. I am terrified. I got mastitis once early PP and clogs often, and have already seen a slight dip in my supply since returning to work. Surely this one-time occurrence won't be the death of me, but what do you all do when this happens? I really don't want to miss any of this meeting as it is extremely important, so excusing myself for 20 minutes to pump does not feel like an option... but I also don't want to be in pain or risk supply issues. I'm guessing the only thing I can really do is feed my baby as soon as I get home from work and pump immediately after...?!

This is turning into more of a vent than a request for advice, but this will surely happen again throughout my breastfeeding journey and it has made me realize one of the reasons so many working moms stop breastfeeding is because pumping at work is so dang hard.