Hi Tim - that is a PITA!!
Might seem onvious, but have you disnantled, dried it out completely, and checked again...it might not be u/s?
If it is, there may be an aftermarket digital panel available (I firget the name, but there was ine that folk with old Hondas bought to replace normal clocks). If not, there are quite a few MTO3s around so a breaker may sort you out for £150?
Meanwhile (and this is a TERRIBLE bodge) a bicycle speedo does do the job for £15, takes a few runs to get accurate, but not too hard. I also had a mate who had a speedo app on his phone, mounted on his bars. Doesnt get you revs, but it might give you time to wait for a second hand panel at the right price.
Good luck.