Trying to recreate this pattern

[jimduggan]

Hello all,

Hope you're having a great weekend.

I'm trying to recreate this pattern using vectors in Xara:



It's a seamless tiling pattern, so it can be placed next to itself in any direction and it will look continuous:



Now, this is how far I've got so far. I'm just using the circle tool, and arranging them one in front of the other:



Everything outside the box can be sliced off later on.

But my question is: does anyone have any ideas about how to do the curvy bit (marked in red), without having to draw it manually?



Thank you for your suggestions!