Urgent visa application

Unfortunately if you don't have a HK-based sponsor then you will have no chance to get a visa by next Monday. A HK visa takes at least 4 weeks to process and that time does not include shipping the physical visa label to your place of residence. The only thing you can do is to talk to your airlines to see if they offer baggage interline service with the other and if they do, you no longer need to go through immigration and thus can complete check-in at the sterile transit area. Otherwise you will have to change your flights.