Dee, I know this thread is long dead but -

I've been seeing some industrial bar-tacking machines from Laramie, WY on craigslist over the past month and just had to post. If you look check the picture of the sewn-off example, it looks like a Alien sling.

denver.craigslist.org/for/3539468474.html

So, I guess if you're willing to pay a bit more for your re-slinging and shipping, you could just do it yourself! Maybe they'd even ship you aliens back with the machines, who knows?

Interesting! Yup, those definitely look like Alien slings!