I've broken two of these things. I got tired of buying new ones and started poking about trying to repair one. It's bit tricky, but you can extend the life for quite a while. Having a bit of skill with a soldering iron and nimble fingers is needed.
You need to cut back the strain relief all the way back to the rounded part of the plug. Don't cut the wires. You'll probably have about a quarter inch of wire left over. Separate the two bundles, strip back the insulation on the incoming wire a bit and solder the two wires together. You'll want to do the middle wire first, wrap it in an inch of electrical tape or so, then do the second one. The wrap the whole thing in another 6 inches of electrical tape (rubber tape if you can find it would work better) and cover the whole thing with a bit of heat shrink tubing. It's all good for another year or so. The electrical tape may move around a bit and you might have to re-do that part of it, but it will work.
If you end up breaking the wires too close to the base you can also break open the end piece. Place a knife or something sharp in the seam between the white part and the clear part. You'll have to cut the little magnet that reduced radio interference out, but with a good application of electrical tape and solder you should have a working adapter.
I take no responsibility for you messing this up and burning down your house. 😀