Lav drain: 1 1/2" with long thread
I'm trying to install a custom-made vessel sink on a concrete countertop. I had the sink made for a 1 1/2" drain (probably should have used 1 1/4" I've just learned). The countertop is 1 1/2" thick. I got a standard 1 1/2" pop-up drain, installed it and it leaked. I think the reason was the there is not enough thread sticking through the countertop to get everything together will the washer supplied.
The sink and countertop are in place so I'm trying to find a 1 1/2" drain with a long thread (e.g. 4"). Does such a thing exist? If so, who makes something like that? I've looked on-line at Home Depot, Kohler, etc. with no luck. I will appreciate any pointers.