Right. On both Expedia and Airbnb they have listings where you pre-pay in full to book but can cancel within 24 hours (or by a certain date) and that has worked for me before for other visa applications.
I’m not certain for the STV of course, because I personally brought a lease for a condo. But could be worth a shot!
I’m sure you could also book on Expedia, Airbnb or other sites where they give free cancellation. So make booking for the required dates, print the confirmation, then cancel.
I have a lease until end of December so I showed the lease agreement. They extended me the full 90 days until end of January even though my lease only goes till end of December so maybe just having a hotel booking will suffice, even if it’s not for the full duration.