The texture of these handwarmers is lovely and similar to a leaf shape. A few yarn suggestions:

1) Rowan Pure Wool Worsted (100g/200m/219yds; superwash wool),
2) Lion Brand Wool-Ease Worsted (180m/196yds; 80% wool, 20% acrylic)
3) Lion Brand Vanna’s Choice (Solids 100g/170yds; 100% acrylic).

The suggested needle size is U.S. Size 1 (2.25mm), which seems small for worsted weight yarn but creates a dense and warm hand covering. Tight knitters may wish to go up in needle size to maintain gauge and/or if knitting these for larger than an average size hand. Loose knitters will likely be fine using the needle size suggested unless the hand warmers are for larger hands, in which case a larger needle is suggested.