Sure!

Happy to help! I am actually working a on a cutter today.
I just called Joe at Speedy and I have some new info, but I will start at the beginning.
To start, I currently use 26 guage food grade stainless steel that I get from Joe.at Speedy Metals. (1-866-938-6061). If you call, tell him that you are from The Cookie Network. (This is just what he calls us cookiers.) After I posted the information last time, he has had several people call to order and several repeat customers as well, so this seems to be working out.
It has been a while since I spoke to him as I placed a large order and am still working through it, but I now have a variety of info/points to share and some new info as well after just speaking to him:
1) I have had good results with the 26 guage SS, but I do not feel that you are not going to get the easy bends that you see that she does with the copper for her shamrock. Copper is more malleable. That is the nature of it. What I have been using is thicker. I would be likely be hard pressed to get that bend on the bottom of the shamrock. Joe cannot get a thinner SS than the 26 guage that I am currently using. I also do not think that the tool she uses to make the holes will work due to how thick it is.
My 1 x 48 strips come to $1.02 per strip plus shipping. Substantially cheaper than copper at 10 feet for $31 plus shipping. 10 feet in SS would be $2.60.
2) I did do a lot of research on this topic and another option I had looked at is to use food safe aluminum. I know that you will get good bends with it as I have seen cutters made with it. I have found it here:
http://www.foosecookiecutters.com/store/cutterkits/index.html
You can get 2 strips 1 of 72 X 1 and (1) of 72 x ½ for $16.95 plus shipping.
I checked and their aluminum is normal aluminum and will rust if not thoroughly dried, so it has not been treated in any way to make it non-rusting. Also, it is not as sturdy as the SS I use. However, it is an option, but
I just called Joe and he is going to send me a sample of aluminum to try with the thoughts of trying something a bit more bendable, bearing in mind that aluminum will rust whereas I do not have that problem with my SS. I do already have a variety of aluminum cutters and to prevent rusting, after I wash them, I pop them in an oven to completely dry and (try not to laugh) put them in Ziploc bags to protect them from humidity (i.e. moisture that would cause rusting). The aluminum (if it works out) will be more malleable and would be $,77 per 1 X 48 strip. Even cheaper than the SS, but again, more bendable, but not as sturdy and rusting can be an issue.
IMPORTANT NOTE: This is not at all the same thing as aluminum flashing that you find at the hardware store. That has been treated with chemicals and oil that make it not at all food-safe, not matter how much you wash it. I called the companies directly and did a lot of research on it, so please do not think it is the same as it is not at all.
I will try the sample of the aluminum and post here what I think in comparison to the 26 guage SS for bendablity. I can see staying with my SS for most shapes as it is so durable and maybe doing the more malleable aluminum for highly intricate shapes.
I will let you know what I think within the week. This thinner option may work with the tool she uses to make the holes to insert the rivets. Again, a brilliant idea. Again many thank you's to Antonia74 for sharing that.