Fresnel Lens for cooking/boiling water

Has anyone considered, or even better, followed through with purchasing a Fresnel Lens solar 'oven'? I'm considering this:

https://www.ebay.com/itm/170859924873#ht_5595wt_1163

If anyone has researched this, I'd love to hear of any alternative vendors. This guy puts up some very informative information, and his product sounds good, but I have been unable to find anyone else selling Fresnel lenses of this size.

Since I live in San Diego, and the sun is bright at least 80% of the time, this seems like a very inexpensive preparedness tool.

Thoughts?