Learn these transformerless power supply circuits, use a capacitor instead, it smaller and lighter than transformer. There are circuits as follows.
More about 9 volts DC power supply or 9V voltage regulator
First choice of Fixed Regulator using family IC-78xx. It is easy to use, cheap, popular for a long time.
Modify power supply source in old circuit PCB. I then build to is 9v regulated power supply circuit , that can give current 1 to 2Amp. Look 3 circuit below
This is Diy digital voltmeter panel meter 0-50V is 0-50V scale. Display with LED 7 segment. In cost 3$ dollar only, builds simple regulator dc power supply