Brian, did you even follow my link yesterday to APT? As well as decent inserts sold in two they have individual holders in a wide range of styles available individually.
I would stick with the CCMT and CCGT types rather than triangles and usually the holders are servicable so don't rush to get rid of them without at least trying with some half decent inserts.
I would suggest these for general use on mild steel and cast iron, yes that's almost £5 an insert with VAT and postage but they work unlike the 25p ones.
And these for non ferrous, stainless steel and more difficult steels
If you want a new 10mm sq holder then a RH one will do both turning along the length of the work and facing the ends so a LH is not really needed. You can also get individual 6, 8 and 10mm Sq from the likes of ARC, Chronos and JB Cutting Tools so no one is conspiring against you
And this is the finish with the fine feed and CCMT060208, don't have an Ra tester like andrew but it passes the reflection test at least in the middle (see Martins comment)
Edited By JasonB on 06/10/2021 16:39:04
Edited By JasonB on 06/10/2021 16:41:36