I'm finding all the paddles I'm trying have the adjustable join right where I grip the bar with my hand. What are my options to find/fix/customise a paddle so the the adjuster is no where near my hand?

my bottom hand is half way down the shaft when paddling for a wave

I have an adjustable Fanatic, your hands are to close together I would guess drop the lower hand further down the shaft?

This might help give you some alternatives.

You're not alone - 6'2 here with longish arms. I have a few paddles, amongst which is an adjustable 2-piece Naish Makani (which I won in a raffle). It's a better-than-decent paddle but with it set at an appropriate length for my lower hand wants to go right where the clamp is. My 5'2 wife doesn't have that problem with it.

I once tried a three-piece RED paddle travel paddle (bit like the one in the vid) where the clamp was further up - no issues with clamp interference there. I think Fanatic also do a three-piece(?)

Depends on how much adjustability you want (that is, how much you want to adjust and how often). I mostly use a couple of Ke Nalu paddles with the extension handle - adjustable yes but needs a heat gun .