Welcome Aboard!
The Lifan KPX 250 would be a perfect fit and is street legal.
https://www.venommotorsportsusa.com/...d-street-legal
There's also the Templar X. Although it an Off-road bike. Some have been able to get them registered and Tagged. I don't think Texas will be any problem.
https://amzn.to/48DOt0m
These are both true 250cc engines with a 6 speed transmission.