Hello,
If you're going down the parts replacement route I have nothing to add.
However as you've said you're not willing to blow money on a truck that you might not keep, I'll share my experience:
It's not a Mistu, but the master cylinder on an old Mazda pickup I have started leaking and I couldn't get parts here in France (import from ZA).
So I had the whole lot apart and scrubbed the bits (piston, rod, cylinder) out with fine wire wool. To save the rubber seals I literally wiped off the perished layer on the lip of the seal with the wire wool. If your seals aren't split it's probably just liquid seeping pas a perished lip.
The whole lot went back together with some synthetic fluid and I forgot about it until I read your thread.
I think It was about 5 years ago.
Took an hour or two as I recall.

If you find a split seal you'd be surprised what a bearing/hydraulic supply shop can come up with to replace it. The whole unit replacement philosophy of the car parts industry annoys me when it's a tiny plastic bitonio that means the whole thingumy has to be replaced!
It annoys me even more as I designed bits for Renaults (NEVER buy one) and my bosses imposed these built in obsolescences because it costs less! They really don't give a toss about product life and customer satisfaction in the car industry, that's the salesman's job to convince the client he did something wrong.
Sorry I'm ranting.
Good luck with your clutch
Luke