Spinning up a Fusionhub Solo (free license) on a cheap cloud server (vultr.com and upcloud.com are favorites - $5/month) will provide you with a static and routable IP address. Then set up a PepVPN/SpeedFusion link from your Balance 20 to the Fusionhub and you’re in business. (There are a number of posts on this and related topics, see for instance Remote access to server behind Peplink Transit router - #2 by MartinLangmaid)
Cheers,
Z