The notepads of the Middle Ages were wax tablets, [like so] (http://i.imgur.com/HQQxKct.png). (Or here is actual 12th century nun Hildegard of Bingen using one in the late 1100s.) Gertrude of Helfta, a late 13th century Rhineland nun and mystical author, used to carry one around with her, so right on your 1290 time frame. They were apparently ubiquitous in medieval convent life. Our nun-visionaries see (in their visions) lots of things written on tablets, in addition to the usual book imagery. That's the closest thing I can think of to something the average nun would have "owned" (reserved for personal use), on account of the poverty vow.

One really cool devotional practice very popular in women's convents at the time was cradle-rocking! Dolls of the Christ-child (in infant form) were carried, cared for, dressed, mock-breastfed (it's a medieval thing), placed in cribs and cradles. This practice of imitatio Mariae (imitation of Mary) was a way for its participants to form a tangible connection to Christ in his most vulnerable humanity. The surviving examples we have of those tend to be extremely ornate, for obvious reasons that those would be the ones preserved. This is a famous 15th century Christ-crib. The average monastic community would not have owned one so fancy, I think, but it gives you an idea if you have woodworking or wooddecorating skills.