Universities do require the original diploma when you submit your documents, but here's one thing people often miss: some institutions allow you to submit a copy of a school completion certificate or a temporary document confirming that you've finished grade 11. It's not a full diploma, but it might work for registering your application - the key is to check with the admissions office of each specific university to see if they accept these documents.
Once you get your final diploma in September, you'll need to provide the original before enrollment. So you can start competing now if the university agrees to a temporary confirmation, but you'll only make it onto the acceptance list after submitting the complete document. Some universities require the original right at the application stage - there's nothing you can do about that, you'll just have to wait until September.
My advice: call the admissions offices of the universities you're interested in and ask directly what documents they currently accept. Rules can vary, and sometimes there are loopholes that aren't immediately obvious.