That is a performance nightmare, suppose you have 100 products, would you really want to make 100 unique SQL queries to the other database? Not a very good idea, your site will drag, and your stakeholder won't be happy ;)
I would preload this data, either to new fields in existing kentico page types, or even to a custom table that maps as close as possible the external database.
On each application start, you load the external database to your kentico database, you could also use cache dependencies -https://docs.kentico.com/display/K8/Setting+cache+dependencies- to make sure this data is refreshed on cache clearing for example.
Or even, create a scheduled task to update the data on a recurrence, https://docs.kentico.com/display/K8/Scheduling+custom+tasks
Then on the repeater (depending on how you store this data) you can either join with the custom table, or use the field in the custom table.
Best of luck, let me know if you need clarification on any of the points above to get you started.