You can use LetsEncrypt for free, and it is very simple to get going.
https://letsencrypt.org/
Edit: Given its running on Apache/Ubuntu by the looks of it, you should be able to get a cert on there in ~5mins.
I do quite fancy one of these but I'm a hamfisted idiot and probably don't have the knowledge/patience to keep it going/sort the niggles.
Sounds like your one is getting better day by day, good work.