Miranda,
Thanks for your question. It is important to use the right sized cuff for taking blood pressure. If the cuff is too tight, the readings will be exaggerated. I would check with a medical supply house to see if they stock a monitor that also makes a large cuff (or thigh cuff if necessary) to work with that machine. If not in stock, ask them to check their suppliers for one that would be suited for you. The next step would be the internet (which I just did a search) which has several sites that supply thigh cuff and monitors. In this case, try to go through a medical supply house so returns and exchanges will be easier should there be a problem with fit.
Best wishes.
Martin Cane, M.D.