Working close to Concord gets me to Whites and Walden at least once/week during lunch. With Wachusett walking distance from my house, I usually hit that on the way to work, but it's difficult to fly fish from shore there and no boats allowed as you know. I can certainly arrange an extra early morning trip to Concord. Whites has too many sunfish in my opinion and there's often too many people and dogs on the side where the train runs. Maybe first thing in the morning is a different scene?
Also, have you fished Long Sought For Pond in Westford? I see no access that's convenient and I'm starting to think it's stocked purely for the enjoyment of that campground that's on the other side from Route 40. But everytime I go by there's not a sole fishing. So, if you have flotation, this may be a pond with many fish. It received 600 rainbow in the fall stocking as well.
I also fish Nashoba Brook in Acton and Concord - always see fish when I arrive and never buy a hit.