Garmin GPS

Search the model number of the card you need on Amazon or eBay. You might find a used card for a good price. You could also find cards that are a year to two old. The roads may have some changes, but the cards could be much cheaper.

Before my May trip to Croatia/Bosnia, I bought an SD Europe map for my Garmin off of eBay for $25. Even though it was "Europe NT 2015.30" it still seemed a little out of date in places.

I think on my next driving trip to Europe I will just use my Android phone and Google Maps.

I don't know how often you'll be traveling in Europe but it might be more economical to get a new Garmin unit with European maps with free lifetime updates already installed. Years ago I bought one of their units with North American and European maps installed. At that time lifetime maps were not part of the purchase. After the one year free update expired, you had to purchase updates and I opted for the NA and Euro lifetime option. I've been using the unit I purchased in 2007 ever since with current maps and poi's.

I would say "lifetime maps" is a waste of money. GPS units are quickly becoming irrelevant as more and more people simply use their phones. My last Garmin (bought in 2012) had "lifetime maps" (only North America on mine), but the GPS itself is already feels obsolete. I'll probably never use it again - so "lifetime maps" meant about three years for me. My new $40 Android phone is light years more advanced in terms of the navigation software, and of course maps are always updated.

I have a Nuvi LM (lifetime maps) for my automobile GPS. The ability to update is in the eye of the beholder. My old GPS didn't have a life time update and when a local interstate interchange was reconfigured, the GPS thought that I was driving across an open field. Roads do change and my current Nuvi also has a data base with services and attractions that do come and go.

With respect to your question regarding SD cards, Garmin does sell uploaded GPS road maps for a number of regions beyond North America:
https://buy.garmin.com/en-US/US/maps/on-the-road-maps/c452-c454-p1.html
For example, the Nordic region cost $69.99 USD and covers:

Features motorways, national and regional thoroughfares and local
roads in the Nordics, specifically Denmark, Finland, Iceland, Norway
and Sweden.