Not sure of the size you are looking for but if you want something deep you could laminate several boards or plywood sheets together then cut the outside in a silhouette of his paw shape or his profile then route out the inside to store the memorabilia. If it only needs to be shallow to hold photos, dog tags... then you could cut the desired shape in a piece of wood then attach it to a backer board, then use a patterning router bit to trim it flush. I’m thinking you can easily cut the profile with a coping saw, band saw, scroll saw...
Sorry for your loss but a great way to remember him.
Saw Dust Rules
“In God we trust. All others bring data.” - W.E. Deming
Dave in Rochester, NY