I had a Lee Big-Stopper filter, which I don’t use much, as my film cameras go into seriously long exposures due to reciprocity effect, but I do use the 10 stop now and then. Well, I used to, because mine shattered to pieces.
I love the Lee filter system. It’s extremely high quality, but I’ve always gotten along fine with the resin filters they do, so I don’t own any glass ones now (broke them all), whereas my resin 3 stop is still going strong after many years of service.
I just learned today that HiTec do a 10 stop filter made of resin, that you can buy (in two variants – one for the HiTec holder and the other for use with a Lee filter holder). I’ve just ordered one and hope it will have many years of service (for the rare times I intend to use it). The good news is that it’s also cheaper than the Lee Big-Stopper too, and it’s widely available. I was able to place an order on Teamwork Photo’s website today for two of them and they’re dispatching tomorrow!
If your Lee Big Stopper is still in one piece, may I suggest you get some hard case for it, to protect it. Mine broke simply because it was in the pouch that Lee provided it in, tucked inside my camera bag. I’ve heard similar stories from others too.