@Pugglt Auld Jock has a favourite garage that is Fiat friendly. Perhaps he might share. It is on lots of his other posts, but would take a bit of time to find.
As said above, more details would be useful.
You seem to have decided on a necessary repair, so some diagnosis may be assumed. So why can the diagnoser not fix it? Are you sure that is the problem? Is it just a gasket failure due to age, or is it a victim to a cause? That could be a good reason why no-one will quote. They need to confirm the diagnosis and cause. If they just replace the gasket, and it fails again, you are likely to hold them liable, which is unfair. From my time in the trade, we would never take a customer's word, we would want to know why. Frequently the cause was not addressed, and often the requested repair was not necessary.
Rather than "can you fix my head gasket", perhaps, "I think my head gasket is leaking, can you look at the cause and advise on the correct repair".
Share your diagnosis path here.