H.W.
Do you have any pictures of your husband and his stepfather? If they got along well, you might consider having a photo enlarged/printed and having that framed for him to remember their relationship.
Youngsters are good at crafty stuff: you could do a photo of your family with an inexpensive frame your daughter could paint with acrylics or decorate with tacky glue and buttons. Are there any sports your family enjoys together? Would it be a fun outing to go bowling or for a hike? (Actually, you may be recovering from childbirth, so never mind!) Is there any outdoor equipment your husband might want like a grill or some new chairs for outside?
You and your daughter could also make a book of Reasons why (Husband's name) is An Awesome Dad.... noticing the times he really helps out, what is meaningful to you/daughter about various interactions (reading together, "I like how you make time to listen..." etc) and how he makes you feel good/supports you as a family. Letting my husband know how much his actions/words mean to us, I know, really helps him feel that his role in our lives is fulfilling and gives him a lot of encouragement.