Configure ClientID transfer to Yandex.Metrica

Task: you need to set up the transfer of conversions to Yandex metric in the form of offline conversions with
Keitaro tracker via ClientID data for the possibility of optimizing advertising campaigns.

Advertising of the site goes through Yandex.Direct, work is carried out with partner networks. But due to the complexity of integrating the metric into the advertisers site - conversions from my streaming link are not recorded in the metric.

The scheme of work is now as follows: the landing page on which advertising goes (on my hosting) - > payment page (streaming link PP). Conversion data needs to be taken from your payment page.

At the moment, a tracker is connected and postback is configured to transfer conversions to the admin panel.

How I see the implementation of the task: for each unique visit to the site, you need to compare the ClientID data from the Metric and the subid data from the tracker. When making a conversion, pull out the subid of this user, and the ClientID that belongs to this sub record in Google Tables for further transmission to Metric.
Or pass the ClientID to the url (as another subid), and when the conversion is made, pull it out with a script.

I will send all the other necessary data in personal correspondence.