so i'm going on a road trip in my 2016 Subaru Forester and need a little extra storage space. It's the base model so the roof is bare... no rails, crossbars or anything whatsoever. one day, I'd like to think I'll upgrade vehicles and whatever I get will at least have a base rack onto which I'd put a Thule box or something similar that I purchase based on my needs at the time. For right not, I just need something quick and cheap to give me a little extra cargo space. In thee past I've rented a Thule 18 cubic foot box for my Subaru Outback... but that ca had the rails and crossbars. This won't work with my current Forester.

I do these trips infrequently enough and know enough people willing to lend their Thule (or similar) box that it doesn't make sense to put the money into a full-blown system. I guess I feel like it would be worth it to put some money into the rails/crossbars, but even they can get crazy expensive. I've heard of ones that attach magnetically that are supposed to be able to hole a Thule box and be 100% reliable... and relatively inexpensive compared to having a factory-like set of rails installed, but I'm having trouble making heads or tails of the billions of products I'm finding with the Google.

Does anyone have any recommendations for either a start-to-finish solution that you know to be safe/reliable and reasonably priced OR an inexpensive way to attach some sort of roof rack (rails/crossbars) that can then hold a box I either borrow from a friend or rent for the week I'll be gone?

I know "reasonably priced" can mean a lot of different things... I guess tell me what it means to you =).

Thanks in advance for any insight or wisdom anyone has to share.