Campfire Time wrote:
The Next Exit is an Interstate traveler's book that lists everything on every exit. It marks the RV friendly gas stations.
"The Next Exit" is a valuable guide for interstates, but alas, not US-90.
Get on Google Earth. You can follow along the highway and look at all the stations from an aerial and a street level view.
For instance, it looks like the Chevron at the intersection of highway 14 and US-90 near New Iberia is a good bet.
Of course, actual experience of some responders is the best.