Just Google graphite blocks for sale:

http://www.ebay.com/bhp/graphite-block

https://www.alibaba.com/showroom/graphite-blocks-for-sale.html

Some discussions of the process on YouTube videos mention band sawing the blocks to thinner slabs. I'm using whole blocks about 1" x 5" x 6" and have not sawn them. Not sure which is better, but I wonder if turning some of the graphite into saw dust puts you ahead.

I paid $100 for 5 blocks that were $0.05 per cubic centimeter. The average price was $0.20, and the highest was $0.83. I needed a spread sheet to find the best deals. My guess is that I have used the blocks mostly every day for 2 months, and they are about 1/3 consumed.

A wading pool about 54" diameter x 10" deep holds 100 gallons, so you can do the math on Evapo-Rust plus some kind of pump and trickle arrangement for big pieces like the dash frame.

If you don't see two dolphins, you need a vacation.