I've looked in the past and would be really keen to do this too. I've got a perfectly fine libre 1 reader which I don't need now my prescription has been changed to libre 2. The key thing is whether the strips etc which go with the device would still be available.
Also got old insulin pens which work fine and would still fit current insulin cartridges, I've just changed to half unit pens. Obviously still advise to keep a spare just in case.