Today, 07:00 AM
I think that a lot of the moms who have switched to just morning/nighttime nursing have older babies, like a year or more. Those babies are eating a lot of solids and have had a year to learn just how much they love nursing. So they're unlikely to give up that source of comfort due to heavy reliance on bottles, as younger babies sometimes do. This is not meant to be discouraging!!! You gotta do what you gotta do, and if that means you are going to need to pump wean and start combo feeding, that's okay.
You definitely can continue to nurse more on the weekends. If your supply really drops, the weekend nursing will need to be supplemented with bottles- you'll be nursing more for comfort, somewhat less for nutrition.
Are you open to nursing at night? One of our working moms here once said something brilliant, which was "Night nursing is a working mom's best friend" when it comes to maintaining milk supply. Adding in a dream feed or two could really help you maintain your supply. I know that's not easy, because obviously sleep is a precious commodity when you are a worki mom! But unfortunately, supply-maintaining tips come in 2 flavors: easy ones that don't really work, and hard ones that do.
ETA: just noticed that you are in Philly. I strongly suggest contacting the Bryn Mawr birth center http://www.lifecyclewomancare.org, and asking them for a recommendation for a LC in your area. BMBC is really trustworthy and they are going to know the right resources...