Macausland Woolen Mills has a nice lap blanket size and they are super warm. You didn't list what country you are in, but they are in Canada. If you are an American , the exchange rate is in your favour. They are quite a bit cheaper than Hudson's Bay or Pendelton and better quality, using wool local to them from the Maritimes and New England. (Pendelton used to buy local wool and stopped, leaving a lot of Oregonian sheep farmers in the lurch and my fam are all still bitter about it)

Otherwise I agree with the electric throw blanket suggestions, or slipping a heating bad under a blanket to warm your thighs and those big blood vessels. Slippers help too, more than you'd think! But what would probably give you the most bang for your buck is a small portable heater pointed right at you.