You can plug into a 50 amp sight but of course you can only draw 30 amps if that is what your TT is fused for.
A dog bone adapter is like chicken soup, it cannot hurt to have one. I have had to take 50 amp sights also but they were all fused and receptacled for 20, 30 and 50 amp plugs.
However, over the last three years I have jettisoned numerous items I was told I could not live without. I simply do not need yet another item to misplace. :)