If weight is an issue, a treadle sewing machine would be out. The cast iron base weighs a ton. Another antique style of sewing machine was a hand cranked machine. It was a table top style. Any of the vintage machines tend to be pricey if you get them somewhere like eBay.
They also have battery operated straight stitch gizmos that sell for less than $50. I have no idea how good they work.
If you've used a sewing machine before you'll notice that you can turn the wheel with your hand to run the needle up and down. That's how the old hand crank machines worked.
If you get a portable sewing machine with a burned out motor that no longer works, you could attach a knob or handle of some kind to the wheel and adapt it to this purpose. If you advertise on freecycle, you might get one for nothing. It isn't the best idea but, especially for traveling with limited space, it might get you by.
Good site, Veme! I was typing when you posted. That site has some instructions for converting the wheel for hand use. I've never done this but it's appealing to think of having something to use when the power is out.
Great info, thanks everyone! Will begin delving into it all.
I've a few uses for it, like stitching medieval costumes, basic repairs, curtains. The hardest is canvas tenting we'll have to do this year. Might just have to bite my own knuckles and buy it ready made (medieval looking, canvas tent).
Janome has a machine for treadle. It's on their web page.
And as to the original question, the type of sewing would not work on any small battery powered machines that I can find.
The next best thing would be the small generator and one of the 3/4 sized sewing machines. I can attest to the work horse costume ability of a Janome Jem 660, and 661 (Gem 2). These have preset stitches but with a jeans needle you should be able to do canvas, I've used the 660 for taking to costume work for school and it did fine, up to 1/2 inch waist bands and then jeans needle seemed to work also. But don't sew feather boa's onto wrist bands, that will make the machine stop after about 12 of them.
The machines are about 12 lbs and can be carried in a med sized carpet bag carrier with one hand easily. The 660 is running $199 online and in shops without the quilt kit, with the quilting kit $249. The 661 is about $200 also. And there is a computerized Platinum 760 that has about 60 stitches and still is about 12 lbs.
And yes, I sew pretty much straight Janome.
I did try the Babylock Xpress - similar in size and features of the 760, but it has a funny feel to it, so I traded it in for a full sized Brother NX600 (when the NX650's were coming out). It's a nice machine, but I still favor the Janomes.
"Live your life, and forget your age." Norman Vincent Peale
Yup, I could do it by hand but seeing how I've a medieval tent that must be used year round in various high wind conditions, rain, storms, AND roughly 8 to 16 medieval outfits to make... um well yeah I'm looking for something faster than hand.