Childrens swim sun hat

[bookbook]

Sorry, not totally sure I am posting in the right place, but you lot are awesome.
Basically my DD is needing help. DGS is 4, but he's a big lad and has a very big head for his age ( the Next age 7-10 sun hat he has is just a tweak small for example )
She is having no luck in sourcing a uv swim hat ( the one with the neck flap) for their holiday in the summer.

I have found one adult one online , but its £20 with the p&p!
Anyone seen any?

My DS, also 4, has a large head. I did buy one from Swimbabes (age up to 6) which stretched to fit his head.

There are some through Regatta for £4.95, not sure if they are water resistant.

Have found a few on Amazon which come in various sizes:
www.amazon.co.uk/gp/aw/d/B0070MY4N0/ref=cts_ap_2_vtp?ie=UTF8&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_p=1212178007&pf_rd_r=8SC3WY4R7E9G98P65KVC&pd_rd_wg=d99lb&pf_rd_s=mobile-detail-softlines&pf_rd_t=40701&pi=SL110&pd_rd_i=B0070MY44E&pd_rd_w=uX81O&pf_rd_i=mobile-detail-softlines&pd_rd_r=8SC3WY4R7E9G98P65KVC&dpPl=1&dpID=41ou65Ue91L&th=1&psc=1&tag=mumsnetforum-21

DD has a Zoggs one which is stretchy?

Thank you!
I did look at zoggs, but the sizes didn't seem to be in stock, but will look with a bit more determination :)