Entering the forest from the "meapole: east side" you have a mint leaves bush.
Bush replenishes when you have 3 or less mint leaves in your backpack.
The only way out is to create as many potions and mint tea as possible. And try to cross the forest without using magic, and get out of the fight if possible
--
If that doesn't help I can give you a fairly simple solution (cheat MP) if you play crt image on Vice emulator.
Backup your crt image file and/or save disk
Run game, Load save
Run Vice Monitor (Alt+H)
m$7e3c (check current value Briley MP)
>$7e3c 50 (set 80 MP points in decimal)
m$7e3c (check current value Briley MP)
close monitor
enjoy
Briley MP $7e3c
Cat SK $7e3d
Mint leaves $7e91
Catmint $7e96
I did not look for other values