HK 416 clone stripped upper/barrel nut/pdw stock

I have a used clone upper, it works but it is not made by HK, and I have replaced my upper with a German made one, forward assist needs to be replaced. It comes with a steel German barrel nut, and a hkparts pdw stock, I cannot locate the buffer/spring but I’m sure it’s available through hkparts. Asking 450.00 shipped.