Like anything, it all depends on how much you want to spend.
You could get something like: Thomann E-Bass Case ABS – Thomann UK or Tourtech ABS Case for a reasonable price. Both will fit most basses, and neither will break the bank.
A Hiscox case would be a great buy, but if you ever sold the TRBX, you would probably be better either keeping the case, or selling it separately.
The big question is, will you be using the case to store the bass and carry it to rehearsals/gigs etc.? Or will you be doing loads of travelling nationally and/or internationally and need a case that'll give your bass that extra protection?