Then don't access any _personal_ accounts from work?
I'm still producing my work, in fact I'm so far ahead of my colleagues, that I can take entire days off because I'm delivering early.
If somewhere told me I flat out couldn't use personal accounts I'd tell them to f- off.
Also - work is give and take - if work is not going to "give" a little, and let me use personal accounts, then I'm not going to "give" you some extra time when production goes down out of hours, or there's a big push for a delivery.
Anywhere that's this inflexible is a crappy place to work, tell them to get bent.
For very sensitive services you're either staying away for 8h/day or use your phone, connected via 3G/4G (not wifi).
You know the saying, my house, my rules :) It's _their_ pc, their internet connection.
Depending on your country, there might be some laws that will prevent them to scan your traffic. Or not.