the best way to find a new friend is by piggy dating at a reputable rescue. that way, the piggy can choose itself who it wants to share its life with (character compatibility is the key to a sucessful bond) and you only come home with another piggy if there has been success; so it minimises the risk. Good rescues will only rehome healthy, properly sexed piggies and any bonding will happen under expert supervision.
We may be able to recommend rescues if you could give us your area. It is really worth going that bit further to a good rescue! I have done so several times with bereaved piggies of mine, always with great success.