(1)I can see "Custom size(Inch)", under "size", please tick it.

(2)If I can't see the , how to pay?

(1) Add your item(s) to cart

click "add to cart"

(2) Proceed to Checkout

click " checkout "

(3) Fill in all the forms and write "custom size" in step 5

write your "make you own costume" requirement on  in step 5.