They aren't illegal to sell. They are illegal to manufacture new ones
for sale in most states.
I was in a Stop and Shop grocery store yesterday and they had two big
pallets of 60 watt incandescents for sale. Same with Home Depot, Lowes
and the local hardware store. I don't live in Texas, BTW.
Texas is allowing the manufacture and sale of incandescent bulbs within their State borders.
Their problem is that they cannot find anyone to actually manufacture the bulbs.
The fact that you don't live in Texas is immaterial.