The more I think about it (it's hard to recommend something I have not used and it's probably the fact that you are having trouble finding what you need that is driving my recommendation), maybe you should go with what's available locally. That way you can add to it and tweak it if needed using the crumble test. The other part that has given me pause is that I went to the manufacturers website and could not find concrete numbers for the concentration of each ingredient. Instead I found a large range of concentration for each ingredient because they do a lot of custom blending. So my concern is that you may get something heavy on peat (which could be problematic and retain too much moisture) instead of it being mostly pine bark based (which would be more desirable for growing Japanese maples in your climate).