Why buy them? Try this ible instead.

That instructable is helpful, but I personally would never use duct tape - it's very heavy and does not contribute to flying. And the bags shown are 0.7 MIL thick, which can fly if the balloon isn't too small (I just released an 0.7 MIL balloon this morning), but I prefer using 0.5 MIL or thinner. My site is http://www.solar-balloons.com/ with instructions for making several different balloon designs, as well as tips & other info, and an online store where you can buy solar balloons if you don't want to make them.

Rather than spamming your site, why not post some ibles here instead?

I was not intending to spam my site - I was merely offering it as a source of information I thought would help you and others out. I do plan to post an instructable on building a 5-foot solar tetroon, which has flown 500 miles in one day. I will do it when I get the pics for it.

I appreciate you posting your site since you have some good DIY info. Thanks.

*bin bags, I wondered if I should've said it in the comment. =)

-thanks for teh link.