First you have my condolences on buying a Street Beast. Although the company has been around for about 30 years it has been in trouble with the Florida authorities almost that long and has changed names at least 4 times that I'm aware of. Do a search on this board for StreetBeast and you will find several discussions about this company's problematic history.
Sorry that I can't help directly with your hinge problem but you might try calling the company to see if they can help. If not, and I expect that's the case, you may have to purchase some aftermarket units and fabricate mounts for them to get everything to work correctly.