tubes

I have a bunch of Hydro sponge filters, and I'm missing uplift tubes for some of them. Anyone know a good DIY solution to make more? I'm assuming its just a matter of finding the right diameter rigid tubing, but wanted to ask if anyone had found something.

Where can I find API 5ml test tube or the equivalent? I had a butter fingers moment and broke 4 at once. If I can find it locally that would be great.