The haramaki, or belly warmer, is a winter staple in Japan. Young and old, men and women, the haramaki does not discriminate (my father was a landscaper, and he used to wear one all the time). I have a few, and they really do keep the belly warm. You can pull them halfway down over your butt, too, so you don’t flash any skin when you bend over in those low-rise pants (slot machine!).
They are just tubes, so they are very easy to make. I got some nice high-tech stretch fabric with fuzzy backing from Rose City Textiles and just sewed one seam (I made my 11″ wide and about 30 cm tall). I did not even bother to finish the cut edges because they do not unravel. Now, with this one (about 11″ wide and more like 40cm tall) I was inspired by a sporty haramaki I saw in a sports shop. Pockets! For gels and keys and such! Genius! I made it as a gift, so I am not sure I got the pocket placement just right, but hopefully the recipient is running miles and miles in the wintry weather with a toasty belly.