space, I agree that your best bet would be a Provi Mini, which, if you didn't mind buying used, you could get for under 100$ these days.
If not a Provi, there are other cheap pocket friendly regulated tube mods, such as the sigelei Mini Zmax. Here's an example, tho I'm pretty sure you can find a better price on it.
https://www.artisanvaporcompany.com/product/sigelei-zmax-mini/?age-verified=80901202cc