Canadian RPN trying to work in USA

I am a Canadian RPN trying to get a license in Texas. I have my green card and had a CES(course evaluation service) done by CGFNS and sent to the Texas board of nursing. They have informed me that certain courses required in the US weren't a part of my curriculum in Canada. No one seems to be able to tell me how to get these missing courses. The colleges I have spoken with will only allow me to enroll for the entire LVN program as opposed to enrolling in just the classes I need to take the NCLEX. Has anyone been through this that can help? Thanks!