You may be able to postpone your court dates until the 7-11 is able to provide the surveillance footage. Otherwise, you may have to go through court to get a subpoena for the tapes.
The Clerk of Courts can issue a subpoena in a criminal case, but you need to provide them with the identity of the correct person to serve it on, and an accurate description of what needs to be produced, as well as a time, date, and location (which court) to appear.
You will then have to pay a process server to attempt expedited service. If it can't be accomplished in time, you should provide the court and the prosecution with advance written notice of the need for an adjournment, and the reason it is required.
Presumably the judge has already warned you about the risks of proceeding without counsel.
This answer is provided for general information only. No legal advice can be given without a consult as to the specifics of the case.