Does anyone know of an SRS account that allows investing in US stocks ?

Can use Endowus to invest SRS money in US ETF at best, cannot for US individual stocks. ETF is a better and safer instrument especially for long term consideration. Several endowus funds support US S&P etf and some included NASDAQ listed companies.

SRS account by design can only invest in stocks/ETFs listed on SGX, or unit trusts. So you can indirectly invest in US stocks by S&P ETF (ticker S27) or US equity unit trusts.