The RedBull racing team creates a lot of video advertising, such as this. When creating these commercials, from where do they get the tyres they use? Do they use the leftover F1 tyres that the team hasn't used in races, or do they obtain them from the supplier (Pirelli), either for free or for a fee?
For types of commercials that you have shown with the Red Bull example, where the car used is not a race car, rather a demonstration car, I would imagine that they are purchased outright, or part of a commercial agreement between the team and the supplier.
An article on racingnews365.com suggests that, even though normal production of the old 13-inch race tyre (which looks to be the tyre used in the RB video) has stopped, Pirelli will continue to supply the older tyres on demand with agreements between the teams and Pirelli themselves:
RacingNews365.com has learned that talks are underway between the F1 teams and Pirelli to continue a small supply of the 13-inch tyres for the foreseeable future.
Pirelli's intent is to produce 13-inch tyres on demand, based on the requests made by the teams – meaning there is not a fixed quantity being kept in stock.
This would ensure a stable supply of suitable tyres for testing purposes such as these older car tests, as well as promotional days. There include events such as demonstration runs that teams (such as Red Bull) host at locations around the world, filming days for sponsors, and any track time the teams decide to do using older cars.
They are not leftover tyres from race weekends as those tyres, used or not, will be returned to the tyre supplier post-race/session - as defined in Section 30 of the Sporting Regulations
30.4 Return of Tyres
a) The official return of tyres will be made electronically using the FIA Race Team Client. In the event of an issue with the system, and when instructed to do so by the FIA, each Competitor will be requested to provide the tyre return data in a CSV file format via email.
b) Any set of electronically returned tyres must also be physically returned to the appointed tyre supplier before the start of the following session.
There are also regulations around "Promotional Events", also called Filming Days. This is where the current race car is driven around for promotional purposes - think: "Here's our new car for this year going around Silverstone vaguely fast", like this one:
From Section 10 of the Sporting Regulations:
10.4 TCC Promotional Events (PE)
a) A Promotional Event (PE) shall be defined as an event in which a Competitor participates purely for marketing or promotional purposes.
b) A PE must not exceed 100km.
c) During any PE, cars must be fitted with the FIA ECU required by Article 8.3 of the Technical Regulations.
d) Only tyres manufactured specifically for this purpose by the appointed tyre supplier may be used.
e) Each Competitor will be permitted to carry out two (2) PE’s with the cars defined in Article 10.1 which will not be considered a TCC
TTC = Testing of Current Cars - defined in 10.1
Given that these types of activities are part of the Regulations, it is reasonable to assume that these tyres are provided as part of the contract with the FIA to be the tyre supplier. Additionally, the tyres provided by the supplier, are to be "demo" tyres, i.e. those that do not meet the specification of race tyres. This is to prevent teams using "Promotional Events" as a means of testing the car.