Hand exercises

My friend recently had a very sudden and painful attack of cellulitis in her hand/arm. After intravenous antibiotics she's much better but has been left with a stiff and painful forefinger which is where the problem started. Consultant has said it's down to her to work through the pain and get the finger moving again. She has an exercise ball but I wondered if there was a hand/finger exerciser which might help-something like a frame/cradle which goes round all her fingers so she can use good ones to help pull down the sore one. Anyone know if there is something like this on the market? I tried google but got a lot of exercise balls. Maybe a specialist physio site ?