We're building 20 sets of bumpers...

[rich2202]

This is what we use:
http://www.robopromo.com/product_p/rp-2006.htm

We are going to make this ourselves, but may decide to order it pre-made:
http://www.robopromo.com/product_p/rp-2015.htm

They also offer a service to put the numbers on for you. Given that we don't know exactly where we want the numbers, we will iron them on ourselves.

With shipping charges to Down Under, maybe your best bet is just to order the numbers, and get the rest locally.