They had the ashes of the Parah for 300 years after the churban – it was only after the cursed Christians expelled us from the land that we lost the ashes – and MUCH more etc…
my Q is: when it’s the right time to build – how will we? the mishna in Parah says that by 2nd Temple they had ashes from that had been brought to Bavel and back (big sugya).
If we need to build in order to have parah, then we have no choice but to go up btuma. and if we DONT need Miqdash for Parah – then why cant we do it now?