Mattress Made To Order?

Hi

This is my first post - please be kind :-)

I have a baby cot without a mattress and am having troubles buying one that fits. My cot is an Australian size baby cot and the size I need is 131x75cm. As you can imagine, it's pretty important I get the right size to prevent the baby from getting stuck in the gaps.

Is there anywhere I can get a mattress made or is there a shop that has them and I dont' know about?

Cheers