Baking – use instead of corn syrup

I saw the question about UK, but I don't think I can find treacle of any kind in Germany.

I am looking for a substitute which will keep the physical qualities of the pie filling reasonably close to the original. I don't mind if the sweetness changes (in fact, I'd probably like it if it is less sweet than the original) and I don't mind introducing new aromas into the recipe.

My first idea was to make a very light caramel, and eventually keep it sticky with a dash of lemon juice. Then I could probably try to solve sugar in maple syrup, which will also introduce a new flavor and also keep it sweet.

Probably the closest thing to real corn syrup sold in the supermarket here is beet sugar syrup. But it isn't high on my list, because I probably won't use the rest up.

I also plan to use walnuts instead of pecans, if it makes any difference (pecans are quite rare here too).

The substitution shouldn't be too adventurous, I am baking this for guests (if I were alone and the filling got too thin or too thick to call it a pie, I'd still eat it as long as the taste is OK).