The best one, in my opinion, is made by SPAAN, who operate out of madrid. Your local bike shop should be able to get one sent from Spain to Italy. Any bike shop in Spain can get you one. While no engine guard will give 100% protection, this one will protect the tank from damage (from personal experience)
If you decide to get one, make sure they send one for the gz250. The one for the gz125 will DEFINITELY not fit!
SPAAN is at :- Tecnoimport S.L., C/ Tajo Nº3, 28840 Mejorada Del Campo, Madrid.
You can also send for their brochure off the internet.