Subaru spare parts

Hello guys, say, where do you buy spare parts for your Subaru? It was quite difficult to find the right middle and rear silencer for my Forester. But beyond that it also needs mounting parts, which are of course not included. Especially the seal which is installed from MSD direction KAT, is (on German sides) nowhere to be found (Subaru part number 44022AA123), as well as the screws, nuts and springs for attaching the MSD are also nowhere to be found. On foreign sides you can find some parts – but a seal for 10-20 dollars plus 25 dollars shipping is just absurd, just like a five pack screws for 27 euros, directly from Japan. So how do you do it with the parts, there must be a way..? mfg N