Does anyone know how to get a recommendation from a warrant officer to go warrant officer?

You just ask someone you admire.  If you are in the situation I was in where I didn't work with a single WO in the unit, contact the senior WO either in your unit or on the post and ask for their help.  That's what I had to do when I was stationed at MacDill AFB.  I got a hold of a CW5 who interviewed me and connected me with a CW3.  I met with him, he interviewed me, took my packet, and asked for a week to review my packet and military history.  I didn't know it at the time but he also went around asking what the folks I worked with thought of me.  It was thorough and I got the LoR.  Sometimes, that's what you need to do.  Also, you can only use a recommendation from a CW3 or higher.

Well, there is the "old fashioned" way, it's not who you know but who you ....

I would imagine if you know one,  just ask them.