You could create them! Have you checked the literature available or even googled it? They could be good as biomaterials for several use provided you have worked on your basics with the bioplastics, how about finding its utility as a biopolymeric bone/cartilage? Good luck!
Yes, you have to search in literature if there are examples of such blends. The main problems when you have to blend PHA with other compounds are the miscibility of them and the diffusion of small molecules also called exudation.
You may try to prepare a coating in solvent such as Hexafluoroisopropanol because HA is soluble in water, while PHAs are soluble in chlorinated solvents. Then the homogenization is very poor. I do believe it is not an easy task but if you find how to do it in a non-toxic solvent let me know. Good luck