Dwight,
Glad you asked. Yes, you could make your own haybox.
for more info go to:
www.thermalcooker.wordpress.com
I am not that industrious. There is alot of info at this site on making your own. Also, a pretty interesting history on hayboxes and how they were promoted as a more fuel efficient method of cooking during the Great Depression. Maybe I should say "the last depression".
The 1.5l from forum appliances is about $70 incl. USPS shipping. They ship the day the order is placed and it will arrive in less than a week. 1.5l is enough for one or two people of many dishes.
When I first got my 3&3 with the optional 6l innerpot I was mistakenly thinking in terms of a slow cooker only. Then after I had it a while I realized I could put cold foods in it, use it as a punch bowl, ice bucket,etc.
The Shuttle Chef/Thermos brand inner pots are heavy gauge SS with a core on the bottom so they make terrific everyday pots for the stove top.
The 6l pot is great for pasta or a larger amount of food. It is the perfect size to make my homemade Kahlua in that I absolutely cannot go without.
As you can see I prefer multi-use items. I really try to avoid things that only serve one purpose.
Have fun at the site I listed and let me know what you think.
'shaker