Truck Repair: gas leak, tank unit, toyota t100

Question
Help,  I have discovered a minor gas leak in my Toyota T100 truck.  It is just dripping out but seems to be coming from the tank itself. I can't see where it is coming from but doesn't seem to be coming from a line.  Is there any additive I can put in the fuel tank that will seal it and not go to the engine?  Or do I have to drop the tank and have fixed by a mechanic?  Any response will be appreciated.

Thanks.  

Answer
Hi Tim,
It could also be from a line on top of the tank, or where the tank unit goes in, but either will require removing the tank, or moving the bed.

No sealant that I know of.
There is a leak repair available at parts houses, but it must be neaded, then pressed into a leak, so you need to find it anyway.

Van