Backup/Secondary DNS and subdomains

I have inherited a host that has a multitude of domains, which does not have DNS redundancy. I signed up to no-ip.com's DNS backup solution to improve this however I have encountered a problem.

One of the domains has various subdomains running under separate cpanel accounts, rather than being created under the primary domain cpanel account. The issue with this configuration is that I would have to register each subdomain at no-ip.com to have zones records backed up - which turns into a costly exercise.

As far as I can see these are my options:

• Manually add each subdomain into the primary website zone (and remembering to update both subdomain and domain zones whenever there is a change). Messy and can lead to conflicting ns records.
• Remove each subdomain account, and recreate under the primarys cpanel. Should be doable, but will need planning and a fair bit of time.
• Run up a cheap vps (ala digitalocean) and host the secondary dns myself

Does anyone else have any suggestions? Im leaning towards a cheap vps to run it.

 

Thanks Michael, I've run up a vps and installed WHM DNS Only.

I've configured the cluster, however I am not sure about the need to setup this new host as a private name server. Step 4 of the initial setup says I have to have two IPs with associated hostnames (ns1/ns2) and register them at the domain registrar - is there any need for this, when the primary host is already configured in this way? Can I just point this dns only server at the primary hosts ns addresses?