I have a Dramm “touch ‘n flow” water wand, a moderately expensive thing which worked very well, except that like so many similar things, the lever valve failed after a few years of age, but little use I might add.
Above, the wand. Note that the handle is molded rubber over some structure that contains the valve… it is designed to be unserviceable.
Above, one can carefully cut the rubber cap off the valve assembly and unscrew the white nylon cap with a 10mm socket. The old spring is shown, rusted and broken into three parts and it would not return the valve to the off position.
The valve spool looks the colour of brass… but on close examination, this one is plastic. Deception, but it is probably better than brass (which is more likely to corrode) which may be fitted to newer wands.
A spring which rusts and the molded covering designed to prevent service is built in obsolescence.
So, cutting the rubber cap off, cleaning the interior of the whole wand (including the rose), a new stainless spring (9mm OD, 1.0mm wire, 20mm long, <$4 for 10 on Aliexpress inc shipping), a bit of silicone grease and reassembly gives a working wand which might outlast the factory job. (Replace the O rings if needed, these were still in good condition.)
Above, the restored valve which is now accessible for service.