The best thing to do is to make your own. What you want is a soil block maker. These can be moderately expensive, but it's also fairly easy to make your own from scratch if you're a little but handy. Just Google "soil block maker" and you'll get lots of hits for instructions on how to make your own and to videos showing their use. Below is a link to one reliable source if you want to get an idea of how much they typically cost. The video on that same page is helpful to watch as it shows how you can use different size cubes to "pot up" if you want to.

Here is a link that might be useful: Soil block maker

One other thing. You might want to read these reviews on Amazon for the tool I linked you to in my previous post as the comments give some helpful tips as well.

Here is a link that might be useful: Soil block maker review