1997 Bravada a/c freon leak

I have a 1997 Bravada and it slowly runs out of freon in about a three weeks or a month. I can add a can or two and it will be fine for a while. I tried a can of the stop leak, no results and even a can of the leak find but never could find the leak. What can I do.
Leak finding can be tricky. Don't use any more leak sealer as it will be the cause of new problems if not already.

Common on these is the shaft seal on the compressor. You might see oil evidence between hub of clutch and nose of body of compressor.

Any where could be a leak but other areas are the condenser from small stones hitting it, "O" rings in line seals at connections, rubber hose lines, THE SERVICE PORTS THEMSELVES ARE A BIG CAUSE, and what you don't want to discover is the evaperator core in the dash. There's a weep hole for water (now know it as condenstate) to drain out slightly towards passenger's side at firewall underhood and if system will make condensate let it drip on clean white paper to see what's in with the water or if you can feel oiliness in the drain that's not so great but you need to know.

It's fast enough it can be found. If dye doesn't show up an electronic detector is the next way to locate the leak,