How often are you switching on/off via the back panel mains switch?
Ideally the box should never be switched off at the mains. In deep standby the box will take less than 0.5W and still wake up for recordings (Approx £2.50/year if left in this mode 24 hours a day for a year @current UK electricity prices)
IF you do switch off at mains the box needs to be fully into deep standby first or else you can corrupt settings.
Replacement switches - assuming the UK
https://www.rapidonline.com/
or
https://cpc.farnell.com/
Search their sites for "miniature rocker switch"
Measure the size of the switch in your box, how many wires go to it, and the mounting method (probably just plastic mounting tabs top and bottom that you push in with a screw driver to remove - the replacement will just push in and the mounting tabs will click into place).
Compare the switch you have with the data presented on that site. Both sites have multiple pages with a large variety of possible suitable switches
https://www.rapidonline.com/Catalogu...switch&Size=20
https://cpc.farnell.com/search?st=mi...switch&gs=true
You want a mains switch 230V,
1 pole if it has two wires SPST (Single Pole, Single Throw) - Single throw just means On/Off
2 pole if it has four wires DPST (Double Pole, Single Throw)
Both the above companies sell to general public but postage on such a small order may/will be in excess of the cost of the item.
Also Ebay will be a source of such a switch - again search for "miniature rocker switch" BUT then check the physical size given in the descriptions.
If you are lucky the wires will be fixed to the switch with spade terminals which just pull off. If you are unlucky the wires will be soldered and you will need some electrical soldering skills. Tip, take a photo of the connections with a mobile phone before you start. Once the wires are removed you then can check the photo to see where they go back