Shower head cleaning 'in situ'

I am in a very hard water area. Had my guest bathroom all re-done a couple of years ago. This involved shower over bath, very large shower head at ceiling height. Cannot find anyway of removing this head,.

Not used very often, but half the holes did not seem to working. Gave it a good clean out (standing on folding stool in bath) with white vinegar and bard of soda. Helped a bit, but not entirely. C

Can see good cleaners on line and at Lakeland, but all say need to soak the head for 20 or 25 minutes in these.

I seem to remember seeing sometime ago, things that could take these cleaners and then be attached to hand round the shower head. Not sure what they are called or where to get them. Any suggestions please gratefully receiving.