The injury-hit Bandits, who had two riders - Manuel Hauzinger and Guglielmo Franchetti - both sidelined with broken collarbones, needed to strengthen their side in preparation for their Premier League campaign, which begins at Mildenhall on Sunday.
Bager, the former Glasgow, Peterborough, Arena Essex and Birmingham rider, was available, and Berwick promoter Peter Waite stepped in to sign him up as a direct replacement for Hauzinger.
And the Bandits' boss couldn't hide his delight at his latest acquisition when he said:
"Potentially, Henning is the biggest signing Berwick has made in the last 15 years.
"He is an experienced rider, and that is what we needed to turn us into a winning side.
"We have made a decent start to the season, but with the league approaching we needed someone like Henning to take some of the pressure off Adrian Rymel and Michal Makovsky at the top of the team."
Bager will make his debut for the Bandits in the Premier Trophy meeting against Glasgow at Shielfield on Saturday.