There is a new challenge type called dns-persist-01 in the works. It is currently in Let's Encrypt Staging system with plans for production this quarter.
I am very sure posh-acme will support that as soon as LE production is ready (as will Certify).
The idea is you create a TXT record once and that persists for as long you like to satisfy cert renewals. That avoids needing a DNS API, acme-dns, and similar.
See: DNS-PERSIST-01: A New Model for DNS-based Challenge Validation - Let's Encrypt
Perhaps the dreaded manual DNS Challenge to get a fresh cert now to carry you until LE has production dns-persist ready? I say dreaded b/c automation is far better but perhaps to avoid having to setup a very temporary new DNS infrastructure it is worth it?