Water Bottle Carrier--I really like this with the extra pocket. I would put a hard bottom in it just for stability.
Coco Rose Diaries: Hot Water Bottle Cover Tutorial
Ravelry: Mixed Stitch Crocheted Hot Water Bottle Cover pattern by Sofie Kay
Hot Water Bottle Covers - Free Knitting Pattern
Cabled hot water bottle cover - free pattern on Let's Knit site
Free Crochet Pattern - "What a Mesh" Water Bottle Holder. Written pattern AND chart!
Hot Water Bottle Cover Tutorial @ Coco Rose Diaries - lovely thank you
Cushion Cover and Hot Water Bottle Sweater / Cover- Cream
LilyRibbons: Hot Water Bottle Cover Tutorial--I like this design, it makes more sense for filling.