Any process that increases the rate, frequency or extent of heparan sulfate proteoglycan biosynthesis. Heparan sulfate proteoglycan biosynthetic processes are the chemical reactions and pathways resulting in the formation of the heparan sulfate proteoglycan, a glycosaminoglycan with repeat unit consisting of alternating alpha-(1->4)-linked hexuronic acid and glucosamine residues.
positive regulation of heparan sulfate proteoglycan biosynthetic process