Where can i buy on line a Ryobi Puk head - Ryobi Expand-It 2 Cycle 26cc Trimmer Power Head

take it apart and fix it

ryobi spares , mower shops , bunnings special counter
e-bay

Hi, I wished I had read this before I bought my rlt1038, I used it for
8 mins and 1) long grass caought around the drive head, 2) I tried to undo the screw holding the line head. Fortunately I have a wide pair of foot prints to go across the line head and a central heating pump adjustable spanner- after 5 mins I had undone it. Yet another bad design !
Good Luck

electric line trimmers suffer from one major design problem
the motor has phosphor bronze bushes and the bottom bush goes dry from the grass juice and wears out and the armature poles out and lacks power to work
to get 5 years is good but it is time to take it in for a service or junk it and get a new one

it sounds like the centrifugal clutch is slipping. take it to several shops and get some quotes. Most times you'll find that fixing a Ryobi is more expensive than buying a bnew one.

You can buy new Line to re-spool on your existing head

The flex shaft drive you are referring to is only sold as a assy that I am aware of. You can try www.partstree.com for the replacement shaft assy. you are refering to, however you may find out by the time you buy a new shaft assy you may be money ahead just buying a new trimmer.
Sorry

There is a nut above the head, place a wrench on the nut then unscrew the head from the shaft, unless yours is different from mine this is how it works. I hope this helps.

Many small line trimmers lack a clutch system by design so this could be normal.