Look at what happens if that non-standard fix fails in six months. You'll have a bigger leak and need the whole job redone, basically paying twice. Waiting for the right sealant might feel slow, but it actually saves you more time and cash later.
Wait, is the two week delay really about the sealant itself? Sometimes the wait is for a certified installer, not just the product. @the_evan is right about the cost of a redo, but the bigger risk is voiding a warranty if you use an unapproved method. That hidden cost can be way worse than a simple leak.