Is there anyway to place a 'hold' of any type on witness needed for other pending criminal cases (in this case in another jurisdiction, ours) that are going to be sentenced to prison in other states or this state?

We would like to place some type of hold so that the witness in our case (defendant in NM) doesn't get sentenced to NM DOC and get transferred to the other side of NM to cut down transport costs.

Are there any suggestions on subpoenaing witnesses from a prison? We have never done this before.

Texas and some states have enacted a uniform statute for producing prisoner witnesses. The Texas statute is article 24.29 of the Code of Criminal Procedure. If New Mexico has also enacted that statute, you should be fine.

If he is currently in a Texas lockup, consider seeking an attachment under ARticle 24.13, which a jail should treat as a hold.