Isn't the best chance that Trump has of getting money for the wall is to veto the bill that Congress will send to him to keep the government?

open? Then leave it to Congress to come up with the 2/3 vote needed override his veto. The Democrats would have to agree to money for Trump's wall in order to get enough Republicans to get that 2/3 vote. It probably wouldn't be the 5.7 billion but it would likely be several billion.
Answers

Clive

That is precisely what caused the shutdown LAST time!

Anonymous

trump could take back 1 / 300 th of the 1.5 trillion tax break for the rich and have his 5 billion .

Justin Thyme

He knows how to get funding if Congressional democrats are too stupid to fund the wall.

Anonymous

Trump has no support in Congress by both parties for another shutdown.