not sure where to find amendments but may I recomend that you stay away from bone meal or blood meal. Both have been associated with health problems. Blood meal is considered a factor in mad cow disease.

The best amendments for Arizona soil are not the ones you mention.

First you need a moisture meter, and a reliable supply of water. Vegetable gardens need stable moisture or the yields drop.

Soil sulfur will lower the pH a bit and make a lot of minerals more available to the plants. The local soil also tends to be high in sodium - a liberal application of gypsum will improve things by locking up the sodium.

Lots of organic materials - anything you can compost - will do more for your soil than anything other additive. Using heavy mulches helps.

Here is a link that might be useful: unimproved desert dirt garden

Looking to buy kelp meal. Where in michigan can I find it?