Spare magazine prices?

[1902MLE]

As far as I’m aware the only mags made for the rifle are all 10 shot so it is what it is.
The most deer I’ve shot at one time is eight but to qualify that it was culling in a deer park, in my stalking rifles I’ll usually load 5 rounds and carry eight spares in a cheek piece and a spare mag with 5 loaded, this is really in case I knock the scope and have to re zero out in the field .