Narrow feet with high arches/instep - help me find flat/comfy summer shoes!

[MyrtleDove]

I'm a shoe size 5.5/6, narrow feet but with high arches and instep - it's proving really difficult to find sandals with enough depth to them to fit my instep, but also aren't too wide. Any ideas? I struggle with heels/high wedges and want something flat for festivals.

I have this but am also size 9-10.
There is NOTHING in my size.

Have tried mail order, London shops, even ordered from the states.

So apart from havainas I have no Summer sandals this year.

Oh gosh that must be an absolute pain!

Myrtle - I have the same size and very narrow but with really low slung arches complete pain in the bum as most sandles are too wide and don't adjust enough for me and too flat so the arches get strained and my knees knock together - awww.

A few years back I bought Flyflot, they're Italian which IME come up narrower than UK sizes.