Thank you all for your replies. The amp is in overall excellent condition and all the components inside are mint. I had it checked, cleaned etc by a technician and it works great.

I keep an eye on another amp like this but as some of you suggested I have posted messages on many forums worldwide that I am visiting regularly, perhaps someone will have the face plate for it one day.

If everything else fail I will consider the refinish of a front panel as Steve suggested.