Custom size options for apparel orders

Using: v1.3.9h, fresh install

I am trying to set up a site with multiple sizes for clothing and I really need a way for the customer to add custom sizes, ie waist, hips, bust etc as one of my suppliers offers a custom fit for larger sizes.

Can anyone help me with this? I've had a look but I couldn't see a way to do it, and search didn't bring anything back either.

You could either use dropdowns for each of the measurements with options like 20", 21", 22", etc., or if you need to allow fractional or very precise dimensions, or lots of possibilities, you could make "text" options where they could type the numbers.

The first method limits the input so it is guaranteed to be meaningful, the second allows freedom, but also the freedom to enter nonsense.