Plumbing/sewer system referrals River Parishes

Looking for referrals on a plumbing company or sewer system troubleshooting that would service the River Parishes. I'm about halfway between Baton Rouge and New Orleans.

Problem - sewer smell in house. Did all of the regular items. Made sure my p-traps were full and my aerator was working properly. Didn't help. Contacted someone in plumbing field and they suggested replacing wax seals on toilets. Did that and had some relief....but I also had my septic system pumped so it was a short lived hiatus. After searching high and low, seems like the smell is trickling down from two bathroom vents in the ceiling (the ones that blow shite smell out of the bathroom after a dump). So I assume I have some type of leak in my vent lines or something. Problem is I have a two story so this area is either hard to get to or inaccessible. So I'm looking for someone to figure it out. I don't know if they will need a snake camera or something or maybe its something else I'm missing. Wife is besides herself and I have no answers. Recommendations or advise is appreciated.