One testicle is enough for the process of reproduction. For cosmetic reasons you can have a prosthesis
inserted into your scrotal sacs. This prosthesis is made of silicon and is completely safe.
No, we cannot put someone else's testis into your scrotum
. If in case your testis was cut because of an accident, then at that time immediately we would be able to replant the testicle using
micro vascular techniques within 6 hours of the injury
. But since your's is an old injury, the best solution would be to go in for a silicon prosthesis which can be inserted by a minor surgical procedure.