I have used the Targus CitySmart EVA Pro for years of heavy road warrior use. If you are dealing with airport security, underseat carry on bag storage (even the A seat in an ERJ135!), etc, there is no better form factor / pocket set than this. And it looks good enough for professional settings as well. Looks like the main padded pocket will fit the frame work with a bit to spare on every edge.
Targus Citysmart Eva Pro Notebook Carrying Backpack 15.6", Gray (2DM64UT#ABA) https://www.amazon.com/dp/B077BRHQY7/ref=cm_sw_r_apan_glt_fabc_JZNR3CPDAJ284SNTZ3HZ