firstly, you should NEVER check for leaks with vacuum!
always pressurize and look with a sniffer or bubbles.
if you have a can of pure 134 you can use it to fill the system with GAS, not liquid. and search for hissing and bubbles. you'll find the leak. a mechanic is going to charge a fortune to fix it, and may not be any better at it than you are.
Nitrogen is the best way to pressurize and look for leaks, but most don't have it available.
you could take it in to a shop and have them pressurize it with N2 and 4oz of R22 and have them sniff for the leaks.