I was going to just make another wheatbag but I thought I'd give hot water bottles a go for a while since they seem to hold the heat for longer.
You will need:
2 old jumpers (or some leftover woolen material).
a sewing machine and thread
a hot water bottle
Draw a love heart shape using a sharpie.
Cut out the love heart using pinking shears.
Trace the hot water bottle shape twice on the other jumper and cut it.
Sew the love heart to the right side of one of the hot water bottle shaped pieces using a zip stitch if possible.
Then put the two right sides facing each other and sew them together.
Trim any excess leftovers using pinking shears.
Then turn it the right way round and put it on your hot water bottle for a pretty cover to hold.
Now all I need to do is warm up some water, make up my hot water bottle and curl up with a good book to read.