Now I think I get what you're after. If I understand correctly what you mean by "price symbol" is a symbol you can use to subscribe to streaming market data for an instrument, right? If this is the case than in Refinitiv terminology this symbol is the RIC. The RIC is what you use to subscribe to streaming market data for an instrument. So if you start with a RIC you already have what you need. If you start with an ISIN you can retrieve the corresponding RIC using ek.get_data('CA01585PAC91','TR.RIC').
ISIN is an issue level identifier whereas RIC is a quote level identifier (it is specific to both the issue and the price source or trading venue). Typically the relationship between ISIN and RIC for a given instrument is one to many. The above call retrieves the primary RIC for the issue. You can also retrieve the full list of RICs for the issue using get_symbology method with bestMatch=False parameter.