A/C drain pan overflowing

[pks]

I have a Gibson central A/C unit. The inside unit has a shallow drain pan and the A frame coils hit the sides of the pan. After the A/C runs for several months a goop accumulates at the edges of the coils where it touched the pan and eventually clogs up and overflows. The pan is only about 3/4 inch deep. Anyone know if Gibson makes a deeper pan I can retrofit into the unit to stop this from happening? Every 6 months or so I have to swing the coil unit out of the housing and lower the drain to clean out the goop (slimy pink sludge). I don't know the model # right now but it's a smaller unit manufactured in 2005 and the filter is 14X20.