You could make it yourself with quick-lime & water to produce slaked lime (Or start with slaked lime).. Then react (mix) that with h202.. Its a pretty simple reaction to get a decent efficiency.. A 1:1 ratio by mass of slaked lime, and 50% H2O2 would be a decent starting recipe, and add however much water you need to get a good mix, but if you want to dry it, be chincy on the water since heating it isn't ideal.. Incomplete reactions would be fine here, possibly even beneficial, since the initial components, and any random products will occur naturally in nature's soil..