Stihl MS261C bar/chain question

My neighbor who owns a tree service gave me this MS261C saw this past weekend as I’ve been cutting/splitting/selling a lot of the wood he has been cutting down, saving him a ton of money on dump fees ($60-$80 a dump trailer).

Long story short, I worked for him for 5 months while I was unemployed and he got the saw as partial payment for a small job he did. He only runs a few Stihl models (201s and 250s) and the rest he runs Husky’s, so he has no want/need for it.

Anyways, it needs a few cosmetic pieces as I was told a log fell on it a year or so ago and broke the top casing (already have a new one ordered). The saw has a 25” bar on it, and not only is it bigger than I really need, it also is too big for the saw as it bogs down big time if you engage more than 2/3 of the bar.

So, I’m looking to get an 18-20 inch bar/chain for it. This is my first chainsaw, and while I have asked my neighbor A TON of questions about it, I’m trying not to be annoying (he did just give me the saw for free). My big question is where can I get a compatible bar/chain? The current bar says it is a 3/8 .050 chain, which I found, but I can’t seem to find a compatible bar that isn’t $80. Any decent cheap(ish) bars? Firewood has become a side gig (I’m an engineer by degree), so it’s not something I’d be relying on for an income or anything, just something to use after work and in weekends.