My local hardware shop still has borax for sale at £1.70 for a 300g box. I did not know that they banned it and can't think why. It is very useful for a multitude of other purposes, but I only use it for deep cleaning my brushes once in a blue moon.
If you wnat some check your local hardware shop first, looking on ebay I notice they are all "Borax substitutes" so it is harder to find that it used to be but not impossible, a bit like the 150W bulbs.
If you really want some and having trouble let me know and I will get a box and send to you.