Look for custom aquarium builders .... I found one in town in the yellow pages under "aquarium & supplies". They advertise custom built glass or acrylic aquariums, and they will repair tanks, replace glass, etc. The price of repairs is rather steep, and in my case, it is cheaper to buy new. <OK, I am in Canada, so our yellow pages might not be the same as yours.>
Alternative is to phone around to some high end salt water lfs
's. Reef tanks tend to be ones needing the most custom work. Certainly the custom tank builders in town are all salt water specialists. <Maybe also post in the SW
PS- if you are brave & a DIYer, there are instructions in the DIY forum on resealing a tank yourself.